IBM SAN storage -- cache battery

filosophizer · May 1, 2011, 5:43pm

Hello,

I have IBM SAN STORAGE DS4100 and one of the cache battery for the controller is dead. Suddenly the performance has been degraded and access to SAN disks ( reading and writing ) became very slow ?

My query: Replacing the battery will take 6 days, so in the mean time what are the ways to speed up the access to the disks ?

1) Could I move the Array from the failed battery controller B to controller A ? Does it need to have multipath MPIO installed and configured ?

2) disable the write cache and enable write-cache working without battery ==> Will it improve the performance ?

3) powering off SAN Storage completely and restarting it ? ==> will there be any implications ?

SUMMARY------------------------------
   Number of controllers: 2
   Number of arrays: 3
   Total number of logical drives (includes an access logical drive): 5 of 1024 used
      Number of standard logical drives: 4
      Number of access logical drives: 1
   Number of drives: 11
   Supported drive types: Fibre (11)
   Total hot spare drives: 0
      Standby: 0
      In use: 0
   Access logical drive: LUN 31 (see Mappings section for details)
   Default host type: AIX (Host type index 6)
   Current configuration
      Firmware version: 06.12.16.00
      NVSRAM version: N1722F600R912V05
   Pending configuration
      Staged firmware download supported?: Yes
      Firmware version: None
      NVSRAM version: None
      Transferred on: None
   NVSRAM configured for batteries?: Yes
   Start cache flushing at (in percentage): 80
   Stop cache flushing at (in percentage): 80
   Cache block size (in KB): 4
   Media scan frequency (in days): 30
   Failover alert delay (in minutes): 5
   Feature enable identifier: 3034383037003834333831004133365E
   Storage Subsystem worldwide name (ID): 600A0B800016E56E000000004133366F


ENCLOSURES------------------------------
 Drive/Controller Enclosure 0 Overall Component Information
      Drive technology: Fibre channel
      Minihub data rate mismatch: No
      Part number: PN 24P8129     
      Serial number: SN 13G6078     
      Vendor: VN IBM     
      Date of manufacture: August 1, 2004
      Enclosure path redundancy: OK
      Fan canister
         Location: Left
         Status: Optimal
      Fan canister
         Location: Right
         Status: Optimal
      Battery status: Optimal
         Location: Controller in slot A
         Age: 858 day(s)
         Days until replacement: 311 day(s)
      Battery status: Removed
         Location: Controller in slot B
         Age: 1055 day(s)
         Days until replacement: 114 day(s)
.....
.....
.....
DETAILS
   Logical Drive name: oraappvg
      Logical Drive ID: 60:0a:0b:80:00:16:e5:6e:00:00:13:1a:41:87:1f:12
      Subsystem ID (SSID): 0
      Status: Optimal 
      Drive type: Fibre Channel
      Enclosure loss protection: No
      Preferred owner: Controller in slot A
      Current owner: Controller in slot A
      Capacity: 135.732 GB
      RAID level: 5
      Segment size: 64 KB
      Modification priority: High
      Associated array: 1
      Read cache: Enabled
      Write cache: Enabled (currently suspended)
      Write cache without batteries: Disabled
      Write cache with mirroring: Enabled (currently suspended)
      Flush write cache after (in seconds): 10.00
      Cache read ahead multiplier: 1
      Enable background media scan: Enabled
      Media scan with redundancy check: Disabled

developerWorks : IBM Systems : IBM System Storage : DS4700 Battery Cache affecting ...
IBM System Storage DS3000 cache batteries not covered under warranty
DS4000 cache battery expiration

Replacing batteries in a DS4300 (FastT600) - IBM: AIX - Tek-Tips
From the storage manager you have to findout the arrays which are pointing to that suspected controller ( say Controller-B) against which the battery is failed.

Now you have to move the arrays from controller-B to Controller-A and make sure while doing this there is no I/O with the disks in the stroage.

It takes little bit of time to move the arrays from the contr-B to contr-A. After this, you have to disable the controller through storage manager. After doing this you can take that module out from DS4300 and replace the battery.

After change the battery, you please put it back into storage DS4300 unit and enable the controller.

After enable the controller, you have to move all the arrays back which you previoulsy moved from Contr.-B to Contr.-A

The Storage Manager Help is pretty staright forward in which you can see the step by step process to change the battery.

---------- Post updated at 01:43 PM ---------- Previous update was at 11:47 AM ----------

I think Multipath is not enabled on the system even though HACMP is installed

# lsdev -Cc disk
hdisk0 Available 1S-08-00-8,0 16 Bit LVD SCSI Disk Drive
hdisk1 Available 1S-08-00-9,0 16 Bit LVD SCSI Disk Drive
hdisk2 Available 1V-08-02 1722-600 (600) Disk Array Device
hdisk3 Available 1D-08-02 1722-600 (600) Disk Array Device
hdisk4 Available 1V-08-02 1722-600 (600) Disk Array Device
hdisk5 Available 1D-08-02 1722-600 (600) Disk Array Device
# lspv
hdisk1 0059da1d0ddcf5b9 rootvg active
hdisk2 0059da1d0d864640 oraappvg active
hdisk3 0059c87d0d80db98 oradbvg
hdisk4 0059c87d7662aa73 None
hdisk0 0059da1d968b4e5f rootvg active
hdisk5 0059c87d27ac212f oradbvg
# lspath
Enabled hdisk0 scsi0
Enabled hdisk1 scsi0

filosophizer · May 5, 2011, 3:23am

The problem was solved by disabling the read and write cache for the disks under the controller which had the failed battery.

I think it could have been solved also by moving the disks from Controller B to controller A , but this I am not sure if you don't have MPIO ( Multi path I/O ) how will it behave ?

I will attach few screen shots later.

thanks