Controlling the speed of RAID operations

Controlling the speed of plex resynchronization

What plex resynchronization is

Plex resynchronization refers to the process of synchronizing the data of the two plexes of a mirrored volume. When plexes are synchronized, the data on each plex is identical. When plexes are unsynchronized, one plex contains more up-to-date data than the other plex. Plex resynchronization updates the out-of-date plex until both plexes are identical.

When plex resynchronization occurs

Data ONTAP resynchonizes the two plexes of a mirrored volume if one of the following occurs:

One of the plexes was taken off-line and then brought on-line later
You add a plex to an unmirrored volume

Modifying plex resynchronization speed

To modify the speed of plex resynchronization, complete the following step.

Step	Action
1	Enter the following command: options raid.resync.perf_impact impact impact can be high, medium, or low. High means that the filer uses most of the CPU time available for plex resynchronization; this setting can heavily impact filer performance. Low means that the filer uses very little CPU time; this setting lightly impacts filer performance. The default speed is low.

Step

Action

Enter the following command:

options raid.resync.perf_impact impact

impact can be high, medium, or low. High means that the filer uses most of the CPU time available for plex resynchronization; this setting can heavily impact filer performance. Low means that the filer uses very little CPU time; this setting lightly impacts filer performance. The default speed is low.

RAID operations affecting plex resynchronization speed

When plex resynchronization and RAID data reconstruction are running at the same time, Data ONTAP limits the combined resource utilization to the greatest impact set by either operation. For example, if raid.resync.perf_impact is set to medium and raid.reconstruct.perf_impact is set to low, the resources utilized by both operations have a medium impact.