Change the RAID from 5 to 0

Discussion in 'Mac Pro' started by alphaod, Nov 19, 2009.

  1. alphaod macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #1
    I have RAID 5 right now. Works fine… I have NVRAM to protect the cache.

    However it crossed my mind recently that I can in fact switch to a RAID 0 and use Time Machine to back everything up.

    Is this a wise choice?

    The Time Machine would be 2x1.5TB drives in RAID 1. The RAID for my internal drives would be 4 drives. The throughput (at least sequentially would be excellent). Only drawback is the rebuild… one failure and I have to restore everything (which can take a while).

    Should I go with this set up? I'm not doing RAID 10 or RAID 6.

    It's just between keeping RAID 5 or going with RAID 0 and backup via Time Machine.
     
  2. pprior macrumors 65816

    Joined:
    Aug 1, 2007
    #2
    Step back and take a breath and answer this one question:

    Why are you doing raid?


    Raid5 and Raid0 have completely different goals in mind. Rarely does anyone consider the two in the same situation.

    raid0 (which really isn't raid...) with 4 striped drives will give you much better performance, but do you NEED that performance? Are you editing uncompressed HD video?

    Raid5 will give you redundancy in case of drive failure - do you need that?

    How much data are you talking about? Can you afford down time to restore terabytes of data from your time machine backup? What happens if your TM backup doesn't restore?

    First define the problems, then the goals, then the solution. Not the other way around.
     
  3. alphaod thread starter macrumors Core

    alphaod

    Joined:
    Feb 9, 2008
    Location:
    NYC
    #3
    I'm going to RAID because I want to maximize performance. That's why I'm not running RAID 10 because throughput on 4 drives in RAID 5 is better. RAID 0 does not offer redundancy, but I can back up. RAID 0 performance is maximized. I keep my most important data backed up like 5 times already.

    My problems include:
    1) 75% available space due to the RAID 5 use of parity.
    2) RAID 5 suffers from the write hole fallacy which is worse than drive failure in RAID 0. Yes the write hole is unlikely, but still possible. I replace my drives pretty often (maybe in 8-12 months), so reliability is less of a concern.
    3) Performance in RAID 5 isn't terrific.
    4) Yes I use my internal disks for scratch with video and images. The more speed the better and I'm not interested in spending more money.
    5) I have 900GB in usable space right now. RAID 0 would increase that to 1.2TB. Restoration would only take a few hours. I think I'm willing to take the risk, but that I won't gain much from the change.
     
  4. sidewinder macrumors 68020

    sidewinder

    Joined:
    Dec 10, 2008
    Location:
    Northern California
    #4
    Only in read-heavy environment. RAID 10 generally performs better than RAID 5 because of the RAID 5 checksum calculation and write penalty.

    S-
     

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