Oracle Exadata Smart Flash Logging

What is Exadata Smart Flash Logging?

In an OLTP environment, it is crucial to have fast response times to redo log writes i.e. low latency.  When multiplexing redo logs for high availability i.e. to protect against hardware failure, redo log writes are only acknowledged when redo is written to all redo log members i.e when the slowest disk completes the write.  By this nature, whenever a disk slows down even if for a moment it can have impact on redo log performance and throughput.

Flash alone can’t resolve this issue as flash can also momentarily slow down due to issues in erase cycles or wear leveling and remember the acknowledgement is only given when the redo is written to all redo log members.

Exadata Smart Flash Logging, is the feature that writes to both hard disk and flash with the acknowledgement given as soon as either completes the write, thus improving response time and throughput.  So if a write is slow to hard disk the flash will give a quicker acknowledgement but when flash is experiencing a slow down due to erase cycles or wear leveling then the hard disk will acknowledge, smoothing out response times.

The Exadata Smart Flash Cache isn’t permanent but a temporary store to provide fast response times by storing redo until it’s safely written to disk.

No changes are required to redo log configuration and is transparent to database and recovery.

How to enable Smart Flash Logging?

It’s enabled out the box or for older systems it’s enabled when applying cell patch version 11.2.2.4 and also requires Database 11.2.0.2 Bundle Patch 11 or higher.

How to disable Smart Flash Logging?

This shouldn’t be done unless instructed to do so by Oracle Support or Development.

How much flash is used by Smart Flash Logging?

By default just 512Mb is used per cell, which should be sufficient for most situations.   It’s a small investment for huge performance benefit.  Statistics record the number of successful write and unsuccessful writes due to the temporary space filled.  In which case the size may need to be increased.  Also I/O Resource Manager (IORM) can be used to disable Smart Flash Logging for none critical databases.

Do standby redo logs use Smart Flash Logging?

Yes, standby redo logs benefit from Smart Flash Logging just as redo logs as long as cell patch 11.2.2.4 or higher is applied and Database 11.2.0.2 Bundle Patch 11 or higher is applied.

How to check that Smart Flash Logging is configured?

Using CellCLI run “LIST FLASHLOG DETAIL” and if output is returned as shown below with the details, then this means that Smart Flash Logging is configured:

[root@v1ex1dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e "list flashlog detail"
 v1ex1celadm01: name: v1ex1celadm01_FLASHLOG
 v1ex1celadm01: cellDisk: FD_00_v1ex1celadm01,FD_01_v1ex1celadm01
 v1ex1celadm01: creationTime: 2015-06-28T17:52:43+01:00
 v1ex1celadm01: degradedCelldisks:
 v1ex1celadm01: effectiveSize: 512M
 v1ex1celadm01: efficiency: 100.0
 v1ex1celadm01: id: 366421ec-bf77-499e-870f-f0cf5390343e
 v1ex1celadm01: size: 512M
 v1ex1celadm01: status: normal
 v1ex1celadm02: name: v1ex1celadm02_FLASHLOG
 v1ex1celadm02: cellDisk: FD_01_v1ex1celadm02,FD_00_v1ex1celadm02
 v1ex1celadm02: creationTime: 2015-06-28T17:52:44+01:00
 v1ex1celadm02: degradedCelldisks:
 v1ex1celadm02: effectiveSize: 512M
 v1ex1celadm02: efficiency: 100.0
 v1ex1celadm02: id: 9f670843-c9cc-4156-a32e-8d23fa79cdb8
 v1ex1celadm02: size: 512M
 v1ex1celadm02: status: normal
 v1ex1celadm03: name: v1ex1celadm03_FLASHLOG
 v1ex1celadm03: cellDisk: FD_01_v1ex1celadm03,FD_00_v1ex1celadm03
 v1ex1celadm03: creationTime: 2015-06-28T17:52:33+01:00
 v1ex1celadm03: degradedCelldisks:
 v1ex1celadm03: effectiveSize: 512M
 v1ex1celadm03: efficiency: 100.0
 v1ex1celadm03: id: 749bada6-8ae2-4c51-8410-97622f9a9532
 v1ex1celadm03: size: 512M
 v1ex1celadm03: status: normal
[root@v1ex1dbadm01 ~]#

For more info:
Exadata Smart Flash Logging FAQ (Doc ID 1372894.1)
Oracle Exadata Whitepaper:  Exadata Smart Flash Cache Features and the Oracle Exadata Database Machine

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Thanks

Zed DBA (Zahid Anwar)

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How to Enable Exadata Write-Back Flash Cache

Please check the following blog post “How to check if Exadata Write-Back Flash Cache is Enabled” for:

  • What is Exadata Write-Back Flash Cache?
  • What are the Performance Benefits of Exadata Write-Back Flash Cache?
  • How to check if Exadata Write-Back Flash Cache is Enabled?
  • Pre-requisites and minimum versions.

You can also get more info from My Oracle Support (MOS) note:
Exadata Write-Back Flash Cache – FAQ (Doc ID 1500257.1)
OTN Article: Oracle Exadata Database Machine – Write-Back Flash Cache

How to Enable Exadata Write-Back Flash Cache

PLEASE NOTE: Although I have illustrated the steps below, please cross check with the MOS note to ensure the method below matches your setup or the steps haven’t changed with future releases (after the time of writing).

With Exadata software 11.2.3.3.1 or higher, it is not required to stop the cellsrv process on the storage cells or to inactivate griddisk.  If you are 11.2.3.2.1 to 11.2.3.3.0, the refer to the MOS notes for additional steps.

It is recommend to enabled Write-Back Flash Cache during a period of reduced workload to reduce the performance impact on the database.

Before proceeding with the enabling of Write-Back Flash Cache, it is recommended to check the caching policy of the grid disks, as we don’t want to enable Write-Back Flash Cache for grid disks that don’t need it i.e. RECO and DBFS disk groups:

[root@v1oex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e list griddisk attributes name,cachingpolicy,cachedby
 v1oex2celadm01: DATAC1_CD_00_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_01_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_02_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_03_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_04_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_05_v1oex2celadm01 default
 v1oex2celadm01: DBFS_DG_CD_02_v1oex2celadm01 default
 v1oex2celadm01: DBFS_DG_CD_03_v1oex2celadm01 default
 v1oex2celadm01: DBFS_DG_CD_04_v1oex2celadm01 default
 v1oex2celadm01: DBFS_DG_CD_05_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_00_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_01_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_02_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_03_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_04_v1oex2celadm01 default
 v1oex2celadm01: RECOC1_CD_05_v1oex2celadm01 default
 v1oex2celadm02: DATAC1_CD_00_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_01_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_02_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_03_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_04_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_05_v1oex2celadm02 default
 v1oex2celadm02: DBFS_DG_CD_02_v1oex2celadm02 default
 v1oex2celadm02: DBFS_DG_CD_03_v1oex2celadm02 default
 v1oex2celadm02: DBFS_DG_CD_04_v1oex2celadm02 default
 v1oex2celadm02: DBFS_DG_CD_05_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_00_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_01_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_02_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_03_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_04_v1oex2celadm02 default
 v1oex2celadm02: RECOC1_CD_05_v1oex2celadm02 default
 v1oex2celadm03: DATAC1_CD_00_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_01_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_02_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_03_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_04_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_05_v1oex2celadm03 default
 v1oex2celadm03: DBFS_DG_CD_02_v1oex2celadm03 default
 v1oex2celadm03: DBFS_DG_CD_03_v1oex2celadm03 default
 v1oex2celadm03: DBFS_DG_CD_04_v1oex2celadm03 default
 v1oex2celadm03: DBFS_DG_CD_05_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_00_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_01_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_02_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_03_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_04_v1oex2celadm03 default
 v1oex2celadm03: RECOC1_CD_05_v1oex2celadm03 default
 [root@v1oex2dbadm01 ~]#

As you can see, all the grid disks have default caching policy.  As per the following MOS note, we disable caching for RECO and DBFS disk groups:
Oracle Exadata Database Machine Setup/Configuration Best Practices (Doc ID 1274318.1)

[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm01 -l root cellcli -e alter griddisk DBFS_DG_CD_02_v1oex2celadm01,DBFS_DG_CD_03_v1oex2celadm01,DBFS_DG_CD_04_v1oex2celadm01,DBFS_DG_CD_05_v1oex2celadm01 cachingPolicy="none"
 v1oex2celadm01: GridDisk DBFS_DG_CD_02_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk DBFS_DG_CD_03_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk DBFS_DG_CD_04_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk DBFS_DG_CD_05_v1oex2celadm01 successfully altered
[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm02 -l root cellcli -e alter griddisk DBFS_DG_CD_02_v1oex2celadm02,DBFS_DG_CD_03_v1oex2celadm02,DBFS_DG_CD_04_v1oex2celadm02,DBFS_DG_CD_05_v1oex2celadm02 cachingPolicy="none"
 v1oex2celadm02: GridDisk DBFS_DG_CD_02_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk DBFS_DG_CD_03_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk DBFS_DG_CD_04_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk DBFS_DG_CD_05_v1oex2celadm02 successfully altered
[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm03 -l root cellcli -e alter griddisk DBFS_DG_CD_02_v1oex2celadm03,DBFS_DG_CD_03_v1oex2celadm03,DBFS_DG_CD_04_v1oex2celadm03,DBFS_DG_CD_05_v1oex2celadm03 cachingPolicy="none"
 v1oex2celadm03: GridDisk DBFS_DG_CD_02_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk DBFS_DG_CD_03_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk DBFS_DG_CD_04_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk DBFS_DG_CD_05_v1oex2celadm03 successfully altered 
[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm01 -l root cellcli -e alter griddisk RECOC1_CD_00_v1oex2celadm01,RECOC1_CD_01_v1oex2celadm01,RECOC1_CD_02_v1oex2celadm01,RECOC1_CD_03_v1oex2celadm01,RECOC1_CD_04_v1oex2celadm01,RECOC1_CD_05_v1oex2celadm01 cachingPolicy="none"
 v1oex2celadm01: GridDisk RECOC1_CD_00_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk RECOC1_CD_01_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk RECOC1_CD_02_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk RECOC1_CD_03_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk RECOC1_CD_04_v1oex2celadm01 successfully altered
 v1oex2celadm01: GridDisk RECOC1_CD_05_v1oex2celadm01 successfully altered 
[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm02 -l root cellcli -e alter griddisk RECOC1_CD_00_v1oex2celadm02,RECOC1_CD_01_v1oex2celadm02,RECOC1_CD_02_v1oex2celadm02,RECOC1_CD_03_v1oex2celadm02,RECOC1_CD_04_v1oex2celadm02,RECOC1_CD_05_v1oex2celadm02 cachingPolicy="none"
 v1oex2celadm02: GridDisk RECOC1_CD_00_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk RECOC1_CD_01_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk RECOC1_CD_02_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk RECOC1_CD_03_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk RECOC1_CD_04_v1oex2celadm02 successfully altered
 v1oex2celadm02: GridDisk RECOC1_CD_05_v1oex2celadm02 successfully altered
[root@v1oex2dbadm01 ~]# dcli -c v1oex2celadm03 -l root cellcli -e alter griddisk RECOC1_CD_00_v1oex2celadm03,RECOC1_CD_01_v1oex2celadm03,RECOC1_CD_02_v1oex2celadm03,RECOC1_CD_03_v1oex2celadm03,RECOC1_CD_04_v1oex2celadm03,RECOC1_CD_05_v1oex2celadm03 cachingPolicy="none"
 v1oex2celadm03: GridDisk RECOC1_CD_00_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk RECOC1_CD_01_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk RECOC1_CD_02_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk RECOC1_CD_03_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk RECOC1_CD_04_v1oex2celadm03 successfully altered
 v1oex2celadm03: GridDisk RECOC1_CD_05_v1oex2celadm03 successfully altered
[root@v1oex2dbadm01 ~]#

Now when we enabling of Write-Back Flash Cache, it will not cache for grid disks for RECO and DBFS disk group, avoiding the need to flush to disk and change policy as post step:

[root@v1oex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e list griddisk attributes name,cachingpolicy,cachedby
 v1oex2celadm01: DATAC1_CD_00_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_01_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_02_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_03_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_04_v1oex2celadm01 default
 v1oex2celadm01: DATAC1_CD_05_v1oex2celadm01 default
 v1oex2celadm01: DBFS_DG_CD_02_v1oex2celadm01 none
 v1oex2celadm01: DBFS_DG_CD_03_v1oex2celadm01 none
 v1oex2celadm01: DBFS_DG_CD_04_v1oex2celadm01 none
 v1oex2celadm01: DBFS_DG_CD_05_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_00_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_01_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_02_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_03_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_04_v1oex2celadm01 none
 v1oex2celadm01: RECOC1_CD_05_v1oex2celadm01 none
 v1oex2celadm02: DATAC1_CD_00_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_01_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_02_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_03_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_04_v1oex2celadm02 default
 v1oex2celadm02: DATAC1_CD_05_v1oex2celadm02 default
 v1oex2celadm02: DBFS_DG_CD_02_v1oex2celadm02 none
 v1oex2celadm02: DBFS_DG_CD_03_v1oex2celadm02 none
 v1oex2celadm02: DBFS_DG_CD_04_v1oex2celadm02 none
 v1oex2celadm02: DBFS_DG_CD_05_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_00_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_01_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_02_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_03_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_04_v1oex2celadm02 none
 v1oex2celadm02: RECOC1_CD_05_v1oex2celadm02 none
 v1oex2celadm03: DATAC1_CD_00_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_01_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_02_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_03_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_04_v1oex2celadm03 default
 v1oex2celadm03: DATAC1_CD_05_v1oex2celadm03 default
 v1oex2celadm03: DBFS_DG_CD_02_v1oex2celadm03 none
 v1oex2celadm03: DBFS_DG_CD_03_v1oex2celadm03 none
 v1oex2celadm03: DBFS_DG_CD_04_v1oex2celadm03 none
 v1oex2celadm03: DBFS_DG_CD_05_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_00_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_01_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_02_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_03_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_04_v1oex2celadm03 none
 v1oex2celadm03: RECOC1_CD_05_v1oex2celadm03 none
 [root@v1oex2dbadm01 ~]#

Next we check that all the grid disks on all storage cells have the asmdeactivationoutcome and asmmodestatus as “Yes” and “ONLINE” respectively.

[root@v1ex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e list griddisk attributes asmdeactivationoutcome, asmmodestatus
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm01: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm02: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
v1ex2celadm03: Yes ONLINE
[root@v1ex2dbadm01 ~]#

Next we check that all of the Flash Cache are in the “normal” state and that no flash disks are in a degraded or critical state:

[root@v1ex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e list flashcache detail
v1ex2celadm01: name: v1ex2celadm01_FLASHCACHE
v1ex2celadm01: cellDisk: FD_01_v1ex2celadm01,FD_00_v1ex2celadm01
v1ex2celadm01: creationTime: 2015-07-01T13:39:22+01:00
v1ex2celadm01: degradedCelldisks:
v1ex2celadm01: effectiveCacheSize: 2.910369873046875T
v1ex2celadm01: id: 655bdb7a-8d3b-40e5-88af-cd42843dd3f7
v1ex2celadm01: size: 2.910369873046875T
v1ex2celadm01: status: normal
v1ex2celadm02: name: v1ex2celadm02_FLASHCACHE
v1ex2celadm02: cellDisk: FD_01_v1ex2celadm02,FD_00_v1ex2celadm02
v1ex2celadm02: creationTime: 2015-07-01T06:38:05+01:00
v1ex2celadm02: degradedCelldisks:
v1ex2celadm02: effectiveCacheSize: 2.910369873046875T
v1ex2celadm02: id: 1cc0f7a4-885a-4e23-aec5-b47bc488e8e3
v1ex2celadm02: size: 2.910369873046875T
v1ex2celadm02: status: normal
v1ex2celadm03: name: v1ex2celadm03_FLASHCACHE
v1ex2celadm03: cellDisk: FD_01_v1ex2celadm03,FD_00_v1ex2celadm03
v1ex2celadm03: creationTime: 2015-07-01T20:39:30+01:00
v1ex2celadm03: degradedCelldisks:
v1ex2celadm03: effectiveCacheSize: 2.910369873046875T
v1ex2celadm03: id: b07f6011-1d66-4c3f-a25f-26d1e6b55633
v1ex2celadm03: size: 2.910369873046875T
v1ex2celadm03: status: normal
[root@v1ex2dbadm01 ~]#

Next we validate all the Physical Disks are in the “NORMAL” state before we modify the Flash Cache:

[root@v1ex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e "list physicaldisk attributes name,status"
v1ex2celadm01: 8:0 normal
v1ex2celadm01: 8:1 normal
v1ex2celadm01: 8:2 normal
v1ex2celadm01: 8:3 normal
v1ex2celadm01: 8:4 normal
v1ex2celadm01: 8:5 normal
v1ex2celadm01: 8:6 normal
v1ex2celadm01: 8:7 normal
v1ex2celadm01: 8:8 normal
v1ex2celadm01: 8:9 normal
v1ex2celadm01: 8:10 normal
v1ex2celadm01: 8:11 normal
v1ex2celadm01: FLASH_1_1 normal
v1ex2celadm01: FLASH_2_1 normal
v1ex2celadm01: FLASH_4_1 normal
v1ex2celadm01: FLASH_5_1 normal
v1ex2celadm02: 8:0 normal
v1ex2celadm02: 8:1 normal
v1ex2celadm02: 8:2 normal
v1ex2celadm02: 8:3 normal
v1ex2celadm02: 8:4 normal
v1ex2celadm02: 8:5 normal
v1ex2celadm02: 8:6 normal
v1ex2celadm02: 8:7 normal
v1ex2celadm02: 8:8 normal
v1ex2celadm02: 8:9 normal
v1ex2celadm02: 8:10 normal
v1ex2celadm02: 8:11 normal
v1ex2celadm02: FLASH_1_1 normal
v1ex2celadm02: FLASH_2_1 normal
v1ex2celadm02: FLASH_4_1 normal
v1ex2celadm02: FLASH_5_1 normal
v1ex2celadm03: 8:0 normal
v1ex2celadm03: 8:1 normal
v1ex2celadm03: 8:2 normal
v1ex2celadm03: 8:3 normal
v1ex2celadm03: 8:4 normal
v1ex2celadm03: 8:5 normal
v1ex2celadm03: 8:6 normal
v1ex2celadm03: 8:7 normal
v1ex2celadm03: 8:8 normal
v1ex2celadm03: 8:9 normal
v1ex2celadm03: 8:10 normal
v1ex2celadm03: 8:11 normal
v1ex2celadm03: FLASH_1_1 normal
v1ex2celadm03: FLASH_2_1 normal
v1ex2celadm03: FLASH_4_1 normal
v1ex2celadm03: FLASH_5_1 normal
[root@v1ex2dbadm01 ~]#

You can run the same command with inverse grep on “normal” to ensure you didn’t miss any disks that are not normal:

[root@v1ex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e "list physicaldisk attributes name,status"|grep -v normal
[root@v1ex2dbadm01 ~]#

Next we drop the Flash Cache to be able to change the attribute:

PLEASE NOTE: Any data that is currently cached in Flash Cache and being served will then need to be served by Hard Disks and a noticeable performance degradation will be observed.  Hence it is recommend to enabled Write-Back Flash Cache during a period of reduced workload to reduce the performance impact on the database.

[root@v1ex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e drop flashcache 
v1ex2celadm01: Flash cache v1ex2celadm01_FLASHCACHE successfully dropped 
v1ex2celadm02: Flash cache v1ex2celadm02_FLASHCACHE successfully dropped 
v1ex2celadm03: Flash cache v1ex2celadm03_FLASHCACHE successfully dropped 
[root@v1ex2dbadm01 ~]#

Next we set the “flashCacheMode” attribute to “writeback“:

[root@v1ex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e "alter cell flashCacheMode=writeback"
v1ex2celadm01: Cell v1ex2celadm01 successfully altered
v1ex2celadm02: Cell v1ex2celadm02 successfully altered
v1ex2celadm03: Cell v1ex2celadm03 successfully altered
[root@v1ex2dbadm01 ~]#

Next we re-create the Flash Cache, which will be in Write-Back instead of WriteThrough:

[root@v1ex2dbadm01 ~]# dcli -l root -g /opt/oracle.SupportTools/onecommand/cell_group cellcli -e create flashcache all
v1ex2celadm01: Flash cache v1ex2celadm01_FLASHCACHE successfully created
v1ex2celadm02: Flash cache v1ex2celadm02_FLASHCACHE successfully created
v1ex2celadm03: Flash cache v1ex2celadm03_FLASHCACHE successfully created
[root@v1ex2dbadm01 ~]#

Next we check the attribute “flashCacheMode” is actually now “writeback“:

[root@v1ex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e "list cell attributes flashcachemode"
v1ex2celadm01: writeback
v1ex2celadm02: writeback
v1ex2celadm03: writeback
[root@v1ex2dbadm01 ~]#

At this point, write I/O will go straight to flash and then can be moved to hard disk if aged or not required for read caching.  The Flash Cache will be repopulated over time and performance will return to normal for reads with addition performance for writes 🙂

You can check the usage increase as Flash Cache repopulates as follows:

[root@v1oex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e LIST METRICCURRENT FC_BY_USED
 v1oex2celadm01: FC_BY_USED FLASHCACHE 104,838 MB
 v1oex2celadm02: FC_BY_USED FLASHCACHE 104,479 MB
 v1oex2celadm03: FC_BY_USED FLASHCACHE 105,192 MB
[root@v1oex2dbadm01 ~]#

Finally, we validate grid disk attributes cachingPolicy and cachedby, where we can see only the DATA disk group is being cached by Flash Cache and by which Flash Disk:

[root@v1oex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e list griddisk attributes name,cachingpolicy,cachedby
v1oex2celadm01: DATAC1_CD_00_v1oex2celadm01 default FD_01_v1oex2celadm01
v1oex2celadm01: DATAC1_CD_01_v1oex2celadm01 default FD_01_v1oex2celadm01
v1oex2celadm01: DATAC1_CD_02_v1oex2celadm01 default FD_00_v1oex2celadm01
v1oex2celadm01: DATAC1_CD_03_v1oex2celadm01 default FD_00_v1oex2celadm01
v1oex2celadm01: DATAC1_CD_04_v1oex2celadm01 default FD_01_v1oex2celadm01
v1oex2celadm01: DATAC1_CD_05_v1oex2celadm01 default FD_00_v1oex2celadm01
v1oex2celadm01: DBFS_DG_CD_02_v1oex2celadm01 none
v1oex2celadm01: DBFS_DG_CD_03_v1oex2celadm01 none
v1oex2celadm01: DBFS_DG_CD_04_v1oex2celadm01 none
v1oex2celadm01: DBFS_DG_CD_05_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_00_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_01_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_02_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_03_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_04_v1oex2celadm01 none
v1oex2celadm01: RECOC1_CD_05_v1oex2celadm01 none
v1oex2celadm02: DATAC1_CD_00_v1oex2celadm02 default FD_01_v1oex2celadm02
v1oex2celadm02: DATAC1_CD_01_v1oex2celadm02 default FD_00_v1oex2celadm02
v1oex2celadm02: DATAC1_CD_02_v1oex2celadm02 default FD_01_v1oex2celadm02
v1oex2celadm02: DATAC1_CD_03_v1oex2celadm02 default FD_01_v1oex2celadm02
v1oex2celadm02: DATAC1_CD_04_v1oex2celadm02 default FD_00_v1oex2celadm02
v1oex2celadm02: DATAC1_CD_05_v1oex2celadm02 default FD_00_v1oex2celadm02
v1oex2celadm02: DBFS_DG_CD_02_v1oex2celadm02 none
v1oex2celadm02: DBFS_DG_CD_03_v1oex2celadm02 none
v1oex2celadm02: DBFS_DG_CD_04_v1oex2celadm02 none
v1oex2celadm02: DBFS_DG_CD_05_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_00_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_01_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_02_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_03_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_04_v1oex2celadm02 none
v1oex2celadm02: RECOC1_CD_05_v1oex2celadm02 none
v1oex2celadm03: DATAC1_CD_00_v1oex2celadm03 default FD_01_v1oex2celadm03
v1oex2celadm03: DATAC1_CD_01_v1oex2celadm03 default FD_01_v1oex2celadm03
v1oex2celadm03: DATAC1_CD_02_v1oex2celadm03 default FD_00_v1oex2celadm03
v1oex2celadm03: DATAC1_CD_03_v1oex2celadm03 default FD_00_v1oex2celadm03
v1oex2celadm03: DATAC1_CD_04_v1oex2celadm03 default FD_01_v1oex2celadm03
v1oex2celadm03: DATAC1_CD_05_v1oex2celadm03 default FD_00_v1oex2celadm03
v1oex2celadm03: DBFS_DG_CD_02_v1oex2celadm03 none
v1oex2celadm03: DBFS_DG_CD_03_v1oex2celadm03 none
v1oex2celadm03: DBFS_DG_CD_04_v1oex2celadm03 none
v1oex2celadm03: DBFS_DG_CD_05_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_00_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_01_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_02_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_03_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_04_v1oex2celadm03 none
v1oex2celadm03: RECOC1_CD_05_v1oex2celadm03 none
[root@v1oex2dbadm01 ~]#

Final note, there is a script provided by Oracle that can do this all for you called setWBFC, however the version 1.0.0.2.1.20160602 didn’t work for me as it detected 4 Flash Disks in eighth rack when it expected 2.  Although there are only 2 in use in eighth rack, there are 4 physically present, so I believe this is a bug.  I did raise an SR with Oracle Support, which is yet to be concluded.  Below is the output for those who are interested:

[root@v1oex2dbadm01 WBFC]# ./setWBFC.sh
 setWBFC Version: 1.0.0.2.1.20160602
 Usage:
 ./setWBFC.sh -g cell_group_file [-d dbs_group_file ]
 [ -h ] [ -i ] [ -l log_directory ]
 [ -m WriteBack | WriteThrough ] [ -o rolling | non-rolling ]
 [ -p ] [ -s step_number ] [ -t time_out_seconds ]
 [ -x trace_level ] [ -v ]

-g file file that lists cell host names, one per line
 -d file file that lists the database host names, one
 per line. Required for non-rolling.
 -h help, print this information
 -i run in interactive mode
 -l log directory directory path for log files
 -m FC_mode flashcache mode: WriteBack | WriteThrough
 -o exec_mode execution mode: rolling | non-rolling (default)
 -p perform a precheck only
 -s step # (*) specify step number to restart at
 -t timeout sec specify in seconds the amount of time to wait
 for griddisks to come ONLINE - range: [600 - 43200]
 Default: 21600 (6 hours)
 -x trace level # specify trace level for further diagnostics
 -v show version

(*) -- Option not yet implemented.

 [root@v1oex2dbadm01 WBFC]# ./setWBFC.sh -g /opt/oracle.SupportTools/onecommand/cell_group -l /root/v1/WBFC/logs -m WriteBack -o rolling -p
 ./setWBFC.sh: Using log directory '/root/v1/WBFC/logs'
 ./setWBFC.sh: Log File '/root/v1/WBFC/logs/setWBFC_18335_2018-01-17-10:46:26.log' created successfully
 2018-01-17 10:46:26
 Starting ./setWBFC.sh on v1oex2dbadm01
 Version: 1.0.0.2.1.20160602
 Command line options used:
 -g /opt/oracle.SupportTools/onecommand/cell_group
 -o rolling
 -m WriteBack
 -p (Perform pre-req checks only)
 -t 21600
 -x 0

2018-01-17 10:46:26
 Performing pre-req checks.....
 2018-01-17 10:46:26
 Creating baseline inventory for griddisks
 2018-01-17 10:46:27
 Creating baseline inventory for flashdisks
 2018-01-17 10:46:28
 Creating baseline inventory for flashsize
 2018-01-17 10:46:28
 dcli present and in PATH. [PASSED]
 2018-01-17 10:46:28
 Checking cell nodes are valid storage servers...
 2018-01-17 10:46:29
 All cells are valid Exadata storage cells.
 2018-01-17 10:46:29
 Checking Exadata Storage Software Versions...
 2018-01-17 10:46:33
 Software versions of the following cells:
 v1oex2celadm01: 12.1.2.3.5.170418 [PASSED]
 v1oex2celadm02: 12.1.2.3.5.170418 [PASSED]
 v1oex2celadm03: 12.1.2.3.5.170418 [PASSED]

2018-01-17 10:46:33
 Checking Grid Infrastructure Software Version...
 2018-01-17 10:46:38
 Grid Infrastructure version: 12.1.0.2.00 [PASSED]

2018-01-17 10:46:38
 Checking for active ASM operations....
 2018-01-17 10:46:38
 Check for no active ASM operations: [PASSED]
 2018-01-17 10:46:38
 Checking griddisk status across all cells....
 2018-01-17 10:46:39
 All griddisks across all cells have asmdeactivationoutcome = Yes
 All griddisks across all cells are ONLINE
 Griddisk checks: [PASSED]
 2018-01-17 10:46:39
 Checking flash cache status.....
 2018-01-17 10:46:40
 Flashcache status normal: [PASSED]
 2018-01-17 10:46:40
 Checking that all FlashDisks are present...
 2018-01-17 10:46:42
 Cell v1oex2celadm01 has one or more FlashDisk missing. Expecting 2 but found 4

2018-01-17 10:46:42
 FlashDisk validation: [FAILED]
 2018-01-17 10:46:42
 Checking current flash cache mode.....
 2018-01-17 10:46:43
 Flashcache not already in target mode: [PASSED]
 2018-01-17 10:46:43
 Pre-req checks failed with status 7. Exiting....

[root@v1oex2dbadm01 WBFC]#

If this works for you, great then I would recommend using this method, otherwise it can be used to double check the pre-requisites at least and then you can do manually as I did shown above 🙂

If you found this blog post useful, please like as well as follow me through my various Social Media avenues available on the sidebar and/or subscribe to this oracle blog via WordPress/e-mail.

Thanks

Zed DBA (Zahid Anwar)

How to check if Exadata Write-Back Flash Cache is Enabled

What is Exadata Write-Back Flash Cache?

Exadata Write-Back Flash Cache provides the ability to cache not only read I/Os but write I/O to the Exadata’s PCI flash on the storage cells.  Exadata storage software 11.2.3.2.1 or higher and Grid Infrastructure and Database software 11.2.0.3.9 or higher is required to use Exadata Write-Back Flash Cache, which is persistent across storage cell restarts.

The default since April 2017 for the Oracle Exadata Deployment Assistant (OEDA) is Write-Back Flash Cache when DATA diskgroup is HIGH redundancy and Grid Infrastructure and Database software are:

  • 11.2.0.4.1 or higher
  • 12.1.0.2 or higher
  • 12.2.0.2 or higher

PLEASE NOTE: This option is only applicable to High Capacity as Extreme Flash doesn’t have Hard Disks and therefore Write-Back Flash Cache is explicitly enabled and can’t be disabled.

What are the Performance Benefit of Exadata Write-Back Flash Cache?

Write-Back Flash Cache can significantly improve write intensive operations because writing to Flash Cache is significantly faster than writing to Hard Disks.  Depending on the workload, write performance (IOPS) can be improved by 10x on older generations of Exadata Machines V2 and X2 and 20x on newer generations X3 onwards (correct at time of writing).

If you are experiencing high write I/O times on storage cells from AWR Reports or Storage Cell metrics, then you should consider enabling Write-Back Flash Cache to alleviate write operations on Hard Disks and move to Flash Cache.

See the following My Oracle Support (MOS) Note for more info:
Exadata Write-Back Flash Cache – FAQ (Doc ID 1500257.1)

How to check if Exadata Write-Back Flash Cache is Enabled?

To check if Exadata Write-Back Flash Cache is enabled, run “list cell attributes flashcachemode” on the storage cell using CellCLI as shown below:

[root@v1ex2celadm01 ~]# cellcli
CellCLI: Release 12.1.2.3.5 - Production on Wed Jan 17 10:09:51 GMT 2018

Copyright (c) 2007, 2016, Oracle. All rights reserved.

CellCLI> list cell attributes flashcachemode
 WriteThrough

CellCLI> exit
quitting

[root@v1ex2celadm01 ~]#

If “WriteThrough” then Write-Back Flash Cache is disabled (writes go straight to hard disk and then can be placed in flash for caching reads if required), otherwise if “WriteBack” then Write-Back Flash Cache is enabled as the name suggests (writes go straight to flash and then can be moved to hard disk if aged or not required for read caching).

You can also run “list cell detail” using CellCLI as shown below:

[root@v1ex2celadm01 ~]# cellcli
CellCLI: Release 12.1.2.3.5 - Production on Wed Jan 17 10:10:22 GMT 2018

Copyright (c) 2007, 2016, Oracle. All rights reserved.

CellCLI> list cell detail
 name: v1ex2celadm01
 accessLevelPerm: remoteLoginEnabled
 bbuStatus: normal
 cellVersion: OSS_12.1.2.3.5_LINUX.X64_170418
 cpuCount: 16/32
 diagHistoryDays: 7
 eighthRack: TRUE
 fanCount: 8/8
 fanStatus: normal
 flashCacheMode: WriteThrough
 id: xxxxxxxxxx
 interconnectCount: 2
 interconnect1: ib0
 interconnect2: ib1
 iormBoost: 6.4
 ipaddress1: 10.1.11.14/22
 ipaddress2: 10.1.11.15/22
 kernelVersion: 2.6.39-400.294.4.el6uek.x86_64
 locatorLEDStatus: off
 makeModel: Oracle Corporation ORACLE SERVER X5-2L High Capacity
 memoryGB: 95
 metricHistoryDays: 7
 notificationMethod: snmp
 notificationPolicy: critical,warning,clear
 offloadGroupEvents:
 powerCount: 2/2
 powerStatus: normal
 releaseImageStatus: success
 releaseVersion: 12.1.2.3.5.170418
 rpmVersion: cell-12.1.2.3.5_LINUX.X64_170418-1.x86_64
 releaseTrackingBug: 25509078
 rollbackVersion: 12.1.2.3.4.170111
 securityCert: PrivateKey OK
 Certificate: Subject CN=v1ex2celadm01.v1.com,OU=Oracle Exadata,O=Oracle Corporation,L=Redwood City,ST=California,C=US
 Issuer CN=v1ex2celadm01.v1.com,OU=Oracle Exadata,O=Oracle Corporation,L=Redwood City,ST=California,C=US
 snmpSubscriber: host=v1ex2dbadm02.v1.com,port=1830,community=public
 host=v1ex2dbadm01.v1.com,port=1830,community=public
 host=v1ex2dbadm01.v1.com,port=3872,community=public
 host=v1ex2dbadm02.v1.com,port=3872,community=public
 status: online
 temperatureReading: 24.0
 temperatureStatus: normal
 upTime: 105 days, 7:35
 usbStatus: normal
 cellsrvStatus: running
 msStatus: running
 rsStatus: running

CellCLI> exit
quitting

[root@v1ex2celadm01 ~]#

However, the simpler way to check is via dcli, especially when you have lots of storage cells as shown below:

[root@v1ex2dbadm01 ~]# dcli -g /opt/oracle.SupportTools/onecommand/cell_group -l root cellcli -e "list cell attributes flashcachemode"
v1ex2celadm01: WriteThrough
v1ex2celadm02: WriteThrough
v1ex2celadm03: WriteThrough

Related Posts:
How to Enable Exadata Write-Back Flash Cache

If you found this blog post useful, please like as well as follow me through my various Social Media avenues available on the sidebar and/or subscribe to this oracle blog via WordPress/e-mail.

Thanks

Zed DBA (Zahid Anwar)

VMware Expert Database Workshop Program Oracle Edition – Day 2

Day 2 kicked off again with another early start at 7am, coupled with the late night, I was a bit tired to say the least, but was all worth it 🙂

Again, it was a very intense day, with lots of presentations and technical deep dives, ending with a lab session:

  • My OCM buddy Yvonne Murphy, kicked the day off by talking to us about “The Best Oracle Support Team on Earth – Global Support Services Oracle Team”
  • Dave Welch, House of Brick, talked to us about “Oracle on vSphere Licensing”
    • Some interesting Oracle license cases of which the main one discussed is available here
  • Jad El-Zein, talked to us about “vRealizeAutomation and Oracle”
  • Andreas Scherr, talked to us about “vSphere Core Storage Fundamentals” & “Modern Converged Storage, & vSAN & vVols”
    • I was impressed with the vSAN concept of using spare drive bays in an ESXi host to put a Hard Disks or SSD Drives in and/or using spare PCIe slots to put a Flash Cards in (including NVMe 🙂 )
    • Then these server attached storage devices are pooled together to provide a shared Datastore that has resilience built in using software rather then hardware 🙂
    • Can be all flash or hybird but each ESXi needs a cache device i.e. SSD Drive or Flash Card
    • More info can be found here
  • Valentin Bondzio, gave us an very enjoyable deep dive on CPU usage in Virtual Environment and how to troubleshoot 🙂
  • We then finished the day with a lab session with Sudhir Bala and Mohan Potheri, where we got to for example:
    • Create a Virtual Hard Drive
    • Attach an Existing Virtual Hard Drive (useful for RAC clusters 🙂 )
    • Then we played a game to stress test a Pure Storage, however I could only get 2Gb a second using 10 sessions running a parallel query of 10 on the largest object in the database.  This is not because the Pure Storage but because of I/O queue in the VMware stack, which we didn’t get time to change but highlight the point 🙂

Another great day of the 3 days workshop, in which I got to gain even more new knowledge in regards to VMware, in particular CPU usage and vSAN 🙂

The day ended with a meal and drinks at The Oliver Plunkett, more socialising with Johannes AhrendsRon EkinsFrits HooglandTim Hall and Mohan Potheri.  Then a nice walk back to the hotel with Mohan PotheriJohannes Ahrends and Martin Klier.  It’s a small world as I found Martin Klier and I had overlap with some customers and people 🙂  The socialising then continued in the reception lounge with Carl Dudley, Ron EkinsFrits Hoogland and Tim Hall.

Many thanks to VMware and Pure Storage, I’m looking forward to the rest of the workshop 🙂

My tweets for the day can be seen here.

The VMware Expert Database Workshop Program hashtag is #VMWORA

My related Blog Posts

VMware Expert Database Workshop Program Oracle Edition
VMware Expert Database Workshop Program Oracle Edition – Day 1

Other related Blog Posts

Tim Hall (Oracle Base) – VMware Expert Database Workshop Program Oracle Edition
Tim Hall (Oracle Base) – VMware Workshop – The Journey Begins
Tim Hall (Oracle Base) – VMware Workshop – Day 1
Tim Hall (Oracle Base) – VMware Workshop – Day 2
Michael Corey (Columnist) – VMware Experts Program Oracle Edition
Michael Corey (Columnist) – Day 1 VMware Experts Program Oracle Edition
Michael Corey (Columnist) – Day 2 VMware Experts Program Oracle Edition

If you found this blog post useful, please like as well as follow me through my various Social Media avenues available on the sidebar and/or subscribe to this oracle blog via WordPress/e-mail.

Thanks

Zed DBA (Zahid Anwar)

Assess Performance using Calibrate on Exadata

For those who are fortunate to have an Oracle Exadata Database Machine, may wonder if their Exadata meets the IOPS/MBPS as per the technical specifications.  Well with the command CALIBRATE in CellCLI, you can run raw performance tests on the cells’ hard disks and flash drives, enabling you to verify the disk/drive performance:

[root@v1ex1celadm01 ~]# cellcli
CellCLI: Release 12.1.2.3.4 - Production on Tue Jun 13 19:02:05 IST 2017

Copyright (c) 2007, 2016, Oracle. All rights reserved.

CellCLI> calibrate force;
Calibration will take a few minutes...
Aggregate random read throughput across all hard disk LUNs: 1823 MBPS
Aggregate random read throughput across all flash disk LUNs: 9973 MBPS
Aggregate random read IOs per second (IOPS) across all hard disk LUNs: 3002
Calibrating hard disks (read only) ...
LUN 0_0 on drive [8:0 ] random read throughput: 152.00 MBPS, and 243 IOPS
LUN 0_1 on drive [8:1 ] random read throughput: 157.00 MBPS, and 246 IOPS
LUN 0_10 on drive [8:10 ] random read throughput: 161.00 MBPS, and 253 IOPS
LUN 0_11 on drive [8:11 ] random read throughput: 157.00 MBPS, and 251 IOPS
LUN 0_2 on drive [8:2 ] random read throughput: 157.00 MBPS, and 244 IOPS
LUN 0_3 on drive [8:3 ] random read throughput: 158.00 MBPS, and 245 IOPS
LUN 0_4 on drive [8:4 ] random read throughput: 156.00 MBPS, and 248 IOPS
LUN 0_5 on drive [8:5 ] random read throughput: 161.00 MBPS, and 250 IOPS
LUN 0_6 on drive [8:6 ] random read throughput: 159.00 MBPS, and 252 IOPS
LUN 0_7 on drive [8:7 ] random read throughput: 158.00 MBPS, and 251 IOPS
LUN 0_8 on drive [8:8 ] random read throughput: 157.00 MBPS, and 251 IOPS
LUN 0_9 on drive [8:9 ] random read throughput: 159.00 MBPS, and 254 IOPS
Calibrating flash disks (read only, note that writes will be significantly slower) ...
LUN 1_1 on drive [FLASH_1_1] random read throughput: 2,157.00 MBPS, and 280525 IOPS
LUN 2_1 on drive [FLASH_2_1] random read throughput: 2,156.00 MBPS, and 274304 IOPS
LUN 4_1 on drive [FLASH_4_1] random read throughput: 2,158.00 MBPS, and 282083 IOPS
LUN 5_1 on drive [FLASH_5_1] random read throughput: 2,160.00 MBPS, and 287786 IOPS
CALIBRATE results are within an acceptable range.
Calibration has finished.

CellCLI>

 

The CALIBRATE FORCE, allows the test to run when CELLSRV is still up, this is acceptable if there is no user workload.  It is therefore recommended to not run during normal operations.  Without the FORCE, the CELLSRV must be shut down.

PLEASE NOTE: This is a single run on a single storage cell, you will need to run on all storage cells in the Exadata Machine to get the total IOPS/MBPS.  You can use dcli to run this across all the cells 🙂

If you found this blog post useful, please like as well as follow me through my various Social Media avenues available on the sidebar and/or subscribe to this oracle blog via WordPress/e-mail.

Thanks

Zed DBA (Zahid Anwar)