Simple RAID 5 Question


I was wondering if it is possible to setup a RAID 5 + Spare without the Spare at first, adding it after the RAID 5 is configured. I am using the areca ARC-1220 PCI-Express x8 SATA II Controller Card as my RAID Controller.


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  1. I have read that already. I'm just not sure if it is possible to add the spare later after the RAID 5 has been built and setup. All that wiki explains is:

    Hot spares
    Both hardware and software RAIDs with redundancy may support the use of hot spare drives, a drive physically installed in the array which is inactive until an active drive fails, when the system automatically replaces the failed drive with the spare, rebuilding the array with the spare drive included. This reduces the mean time to recovery (MTTR), though it doesn't eliminate it completely. Subsequent additional failure(s) in the same RAID redundancy group before the array is fully rebuilt can result in loss of the data; rebuilding can take several hours, especially on busy systems.
    Rapid replacement of failed drives is important as the drives of an array will all have had the same amount of use, and may tend to fail at about the same time rather than randomly. RAID 6 without a spare uses the same number of drives as RAID 5 with a hot spare and protects data against simultaneous failure of up to two drives, but requires a more advanced RAID controller. Further, a hot spare can be shared by multiple RAID sets.
  2. That depends on the RAID controller, and I'm not familiar with the one you're using. But if the RAID controller supports a hot spare drive then I'd be pretty surprised if you couldn't add one at any time.
  3. I have a few Areca raid cards and I am certain you can add a hot spare. Just go into the raid manager and there will be an option to create a hot spare.
  4. for anything important your best bet is to do it right the first time and have the spare available *before* building the array etc
  5. Best answer
    The option you're looking for in the config utility should be migration to "RAID 5E". As sminlal has said, if a card supports RAID 5E then it's almost certain it can do a migration from RAID 5 as the two are almost the same except the offline hotswap.
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