13.14 Restriping a Software RAID

In general, there are three reasons for restriping of software RAID 0 and 5 devices:

  • Partition Replacement: If a partition fails, you must replace it. Restriping can recover the data in a single lost partition in a RAID 5 by using parity. However, the data must be restriped from a backup tape if a partition fails in a RAID 0.

  • RAID Expansion: If you expand a RAID 0 or 5 device, the RAID restripes the data across all members.

  • RAID Stripe Size: If you increase or decrease the stripe size of a RAID 0 or 5 device, the RAID restripes the data across all members. This happens infrequently, unless you are measuring performance with different striping sizes to determine which best fits your operational needs.

If the restriping process is interrupted, the RAID recognizes that when the system reboots, and automatically continues the restriping process. You can also use iManager to pause and resume a restriping process.

IMPORTANT:If the RAID is on a shared system and no NSS pool is on it, it will not restart automatically after a reboot. In this case, the RAID must be enabled using the nlvm raid enable <raid_name> command. Ensure that the RAID device is enabled on one node only. Carelessly enabling a RAID device can lead to corruption.

When expanding a RAID 5, if the newly added drive goes down during the restripe, the restriping continues without the new partition and puts the RAID in a degraded state with one partition missing. If the same partition comes back online, it finishes the restripe. If the partition has completely failed, after the degraded restriping is complete, you can add a new replacement partition, and the RAID restripes to fix it.

To manually resume or pause the Restripe process:

  1. In iManager, click Storage > Software RAIDs.

    For instructions, see Section 9.1.5, Accessing Roles and Tasks in iManager.

  2. Select a server in the eDirectory tree where you are logged in.

    For instructions, see Section 9.1.6, Selecting a Server to Manage.

  3. Make sure that there is no I/O for the volumes on the RAID device by deactivating the volume.

    1. Click Volumes.

    2. Select the volumes in the RAID device you want to expand.

    3. Click Dismount.

  4. Select a device in the Software RAIDs list.

    Wait for the page to refresh before continuing.

  5. Click Restripe.

    The restriping process begins or pauses immediately. Restriping severely degrades I/O performance until the restriping is complete.