Configure RAID |
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RAID (Redundant Array of Independent Disks) Level 4 is used on the filer to ensure data integrity even when one of the disks fails. With RAID, Data ONTAP reconstructs the data from a failed disk using data from a parity disk and transfers the data to another disk, thereby ensuring file access.
This window enables you to determine how RAID works on the filer.
The following is a list of RAID configuration fields and a description of each.
Specifies the time, in hours, that the filer should run in degraded mode before an automatic shutdown.
A filer is in degraded mode if either of the following conditions are true:
One disk in any volume has failed.
The batteries on the NVRAM card are low.
The RAID Timeout value must be the same on both filers in a cluster; otherwise, takeover might not occur properly.
Specifies the speed of RAID reconstruction.
You can select from low (slowest), medium, and high (fastest) speeds from the pull-down list. The filer uses the speed you specify to determine the percentage of CPU time used for RAID reconstruction. Because RAID reconstruction consumes CPU time, sometimes increasing the speed of reconstruction slows down the filer's network operations.
The default speed is medium, meaning approximately 40% of the CPU time is used for RAID reconstruction.
Cluster considerations
The RAID Reconstruct Speed must be the same on both filers in a cluster; otherwise, takeover might not occur properly.
Specifies whether RAID scrubbing should be enabled or disabled. The default value for this field is Yes, enable RAID scrubbing.
RAID scrubbing is a procedure the filer uses to increase data availability. The filer scans each disk in the RAID group for media errors and, if errors are found, tries to fix them by reconstructing the data from parity and rewriting the data.
RAID scrubbing reduces the possibility of a failure of two disks within the same RAID group. RAID cannot recover from a disk media error if there is already a failed disk in the same RAID group.
The scrubbing process runs only while the filer is in normal mode; that is, the filer scans the disks only when all disks are operational. Although scrubbing slows the filer, network clients do not notice the change in the filer's performance because scrubbing starts automatically at 1:00 a.m. on Sunday when most filers are lightly loaded.
Disable scrubbing if you have a recurring problem that scrubbing encounters. For example, there might be an unrecoverable error on a disk that you cannot fix before the next scrub.