Disk replacement for IBM Storage Scale System

You can use the IBM Storage Scale System GUI for detecting failed disks and for disk replacement.

When one disk fails, the system rebuilds the data that was on the failed disk onto spare space and continues to operate normally. However, the performance is slightly reduced because the same workload is shared among fewer disks. With the default setting of two spare disks for each large declustered array, failure of a single disk would typically not be a sufficient reason for maintenance.

The system might continue to operate in the presence of several disk failures even if there is no remaining spare space as long as the number of failures is less than the configured vdisk fault tolerance. The next disk failure would make the system unable to maintain the redundancy that the user requested during vdisk creation. A service request is sent to a maintenance management application that requests replacement of the failed disks, and specifies the disk FRU numbers and locations.

Call home for disk maintenance is requested when the number of failed disks in a declustered array reaches the disk replacement threshold. By default, the replace threshold is one if the number of data spares is zero or one, or two if the number of spares is two or greater. The maximum value is one more than the number of spares.

You can replace the disk either manually or with the help of directed maintenance procedures (DMP) that are available in the GUI. The IBM Storage Scale System GUI lists events in its event log in the Monitoring > Events page if a disk failure is reported in the system. Select the gnr_pdisk_replaceable event from the list of events, and then select Action > Run Fix Procedure from the menu to start the replace disk DMP in the GUI. For more information, see Replace disks.

Disk maintenance is done by using the mmvdisk pdisk replace command with the --prepare option for IBM Storage Scale System recovery groups, which:
  • Suspends any functioning disks on the carrier if the multi-disk carrier is shared with the disk that is being replaced.
  • If possible, powers down the disk to be replaced or all of the disks on that carrier.
  • Turns on indicators on the disk enclosure and disk or carrier to help locate and identify the disk that needs to be replaced.
  • If necessary, unlocks the carrier for disk replacement.
After the disk is replaced and the carrier is reinserted, the mmvdisk pdisk replace command powers on the replacement disk, and integrates it into the IBM Storage Scale System recovery group.