Tuesday, 11 October 2022

Exadata Storage : Grid disks based on the OFFSETs.

The Cells storage servers in Exadata offer the capability to create grid disks based on their offsets, Create the new grid disks in the order BASED ON THE OFFSET, using the sizes shown from the command list griddisk attributes name,size,offset.  

Lets see how we can do it : 

An example :

CellCLI> create griddisk DATA_CD_07_<Host Name> celldisk=CD_07_<Host Name>,size=220G

CellCLI> create griddisk RECO_CD_07_<Host Name> celldisk=CD_07_<Host Name>,size=308.6875G

CellCLI> create griddisk SYSTEMDG_CD_07_<Host Name> celldisk=CD_07_<Host Name>,size=29.125G

Run the previous query on the new grid disks and make sure all the offsets are matching (in the third column):

CellCLI> list griddisk where celldisk=CD_07_<Host Name> attributes name,size,offset

         DATA_CD_07_<Host Name>                 220G                32M

         RECO_CD_07_<Host Name>                 308.6875G           220.046875G

         SYSTEMDG_CD_07_<Host Name>             29.125G             528.734375G

 At the ASM level, the old disk was likely dropped because the disk drop timer has expired.  Log into +ASM1 instance and add the new disk.  Set the rebalance power higher (11) to perform faster and specify the failgroup if the default (name of Storage Server) is not used.

sql> alter diskgroup data drop disk DATA_CD_07_<Host Name> force;

sql> alter diskgroup data add {failgroup <FAILGROUP>} disk 'o/*/DATA_CD_07_<Host Name>' rebalance power 11;

Do the same for RECO and SYSTEMDG from a different ASM instance (to balance the work) or wait until DATA finishes on +ASM1.

If after disk replacement old celldisk and griddidsk are in state proactive failure or any other that prevents them from being deleted, try the following:


celcli> alter lun {lun number} reenable force

for example :

celcli> alter lun 0_0 reenable force

After this, delete cell and griddisks that corresponds to the physical disk

(it may be even done automatically).

Next, create cell disk and griddisk.

Finally after griddisks are created they should be presented in ASM but marked as candidates, but will need to be enabled. 

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