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Maxthon Chan
Asked: 2016-01-14 06:56:45 +0800 CST

How to estimate the time taken by RAID rebuild?

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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).
hardware-raid

1 Answers

  1. Best Answer

    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

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