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I was being stupid and when smoke testing my storage server I forgot to plug in the power of one of its drives (D'oh!) Now I am stuck in rebuilding the RAID-5 array. (Thank god it is RAID-5 or I could have lost a few TB worth of data)

How can I estimate the time it would take to rebuild the entire array?

More details about my setup:

  • RAID card: LSI 3ware 9750-8i
  • HDDs:
    • HGST HUA5C3030ALA640
    • WDC WD30EFRX-68EUZN0
    • WDC WD30EFRX-68EUZN0 (this one was unplugged and rebuilding)
  • Rebuild priority is high (5).
Maxthon Chan
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  • Does it matter how long it will take? The figure will depend on a few factors, so there's no good answer we can give you, since the conditions are specific to your setup. – ewwhite Jan 13 '16 at 16:09
  • Wait until the admin utility shows rebuild 1% complete, then multiply elapsed time by 100 to get a rough estimate of time for rebuild completion – BlueCompute Jan 13 '16 at 17:56
  • @ewwhite Rebuilds like this WILL compete with other IO and a degraded array means I cannot delete the temporary backup yet. – Maxthon Chan Jan 13 '16 at 18:26
  • If this is sensitive data, Raid5 is not a good choice for large drives. Raid6 or Raid-Z (zfs) is much better. The potential for data loss during rebuild if another drives fails is always a concern. – Gmck Jan 13 '16 at 20:07
  • @Gmck I don't have that many drives or I would have been using RAID-10 (faster and pretty reliable) – Maxthon Chan Jan 13 '16 at 20:09

1 Answers1

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3TB drives = 3,000,000MB / 110MBps = approx. 430 min or 7.5 hours. This is just an estimate based on the WD Red average write speed of 110MBps from some published benchmarks at http://hdd.userbenchmark.com/WD-Red-3TB-2012/Rating/1386.

If the array is still in use, then the rebuild will be competing with normal IO operations. If the array was heavily loaded before the disk was unplugged, then the rebuild could be very slow and extend the rebuild time considerably.

You can use LSI's 3dm2 utilities to view the progress. You can find the downloads at http://www.avagotech.com/products/server-storage/raid-controllers/3ware-sas-9750-8i#downloads

Gmck
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