RAID 5 hadn’t a specifies spare disk

Posted July 24, 2021 205 views
DebianBlock StorageStorageDebian 9

On RAID 5 a spare disk wasn’t specified. So does not it matter if the parameter spare-devices isn’t used on CREATE? So which disk will be used as spare?

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You do not have to specify a spare disk during creation of RAID 5. RAID 5 can still work when one of its disk fails.
Although you do not have to have a spare drive in RAID 5, there are two good reasons to consider having it:

  1. The performance of RAID 5 decreases dramatically in degraded state (when one disk fails). Performance stays low until you replace a disk and its content is rebuilt again. If you have a spare disk in your RAID 5 configuration, the performance is decreased just for the time when disk content is being rebuilt.
  2. Having a spare disk in your RAID 5 configuration mitigates a risk of data loss. Imagine the scenario when you get one disk failed, and before you replace it the other disk fails as well. You loose your data then.