Background tasks

While IBM Storage Scale RAID primarily performs NSD client read and write operations in the foreground, it also performs several long-running maintenance tasks in the background, which are referred to as background tasks.

The background task that is currently in progress for each declustered array is reported in the long-form output of the mmvdisk recoverygroup list --dammvdisk recoverygroup list --da command. Table 1 describes the long-running background tasks.

Table 1. Background tasks
Task	Description
`repair-RGD/VCD`	Repairing the internal recovery group data and vdisk configuration data from the failed disk onto the other disks in the declustered array.
`rebuild-critical`	Rebuilding virtual tracks that cannot tolerate any more disk failures.
`rebuild-1r`	Rebuilding virtual tracks that can tolerate only one more disk failure.
`rebuild-2r`	Rebuilding virtual tracks that can tolerate two more disk failures.
`rebuild-offline`	Rebuilding virtual tracks where failures exceeded the fault tolerance.
`rebalance`	Rebalancing the spare space in the declustered array for either a `missing` pdisk that was discovered again, or a new pdisk that was added to an existing array.
`scrub`	Scrubbing vdisks to detect any silent disk corruption or latent sector errors by reading the entire virtual track, performing checksum verification, and performing consistency checks of the data and its redundancy information. Any correctable errors found are fixed.