Is LSI rebuilding as background task

Question

I'm investigating the state of an LSI raid array that might have recently suffered a drive failure. The array had a spare configured, so the array is not degraded. However, the storcli command ( /opt/lsi/storcli/storcli /c0/e252 show ) shows that 2 of the drives have a background task (BT:Y) running.

Does that mean it is rebuilding? What would a background task be?

-----------------------------------------------------------------------------
DG Arr Row EID:Slot DID Type   State BT      Size PDC  PI SED DS3  FSpace TR
-----------------------------------------------------------------------------
 0 -   -   -        -   RAID10 Optl  N  10.915 TB dflt N  N   dflt N      N
 0 0   -   -        -   RAID1  Optl  N   5.457 TB dflt N  N   dflt N      N
 0 0   0   252:0    3   DRIVE  Onln  N   5.457 TB dflt N  N   dflt -      N
 0 0   1   252:1    5   DRIVE  Onln  N   5.457 TB dflt N  N   dflt -      N
 0 1   -   -        -   RAID1  Optl  N   5.457 TB dflt N  N   dflt N      N
 0 1   0   252:2    6   DRIVE  Onln  Y   5.457 TB dflt N  N   dflt -      N
 0 1   1   252:3    7   DRIVE  Onln  Y   5.457 TB dflt N  N   dflt -      N
-----------------------------------------------------------------------------

Is there a way to find out what those 2 drives are doing in the background?

Answer 1

A background task is one you can issue without impacting array availability - ie: during normal operation.

Array rebuild is such a task, as you can continue using the array during the reconstruction. storcli even has the rebuildrate command to select the rate, in percentage, of the background rebuild task.

However, when a disk rebuilds, its state should be Rbld, while you have Onln. Maybe the rebuild already finished (or never happened) and now the two disks are being checked by a patrol read, which is another background task.

Anyway, you should be able to use the show rebuild command to get the current rebuild state. As always, be sure to triple check your commands to avoid any unexpected issues.

Answer 2

Usual background tasks that involve Onln drives are consitency check and partrol read. They are used to detect silent bad blocks that aren't referenced often and so to detect failing drives early, or when information was damaged for some reason (e.g. a bit error) and the RAID redundancy syndrome needs recalculation.

To see if it's ongoing, use:

storcli /cx show patrolRead
storcli /cx show cc