Raid Help Needed

Discussion in 'Mac Pro' started by Tazdaman, Jun 27, 2012.

  1. Tazdaman, Jun 27, 2012
    Last edited: Jun 27, 2012

    Tazdaman macrumors newbie

    Jun 17, 2007
    Hi All,

    I think I have potentially made a huge mistake and would love some help.

    I have a Mac Pro late 2009 with 1 X 250 GB SSD (OS and Applications), 4 x 2TB drives within my Mac, of which 2 are RAID 0 (Western Digital Black) for my video work and the other 2 are raid 0 and used for time machine (Western Digital Green).

    I needed more space so I purchased 2 x Western Digital 2 TB Black drives and I purchased 3 x 2TB Green Drives.

    My plan was to take out the current 2 Green Drives in my MAC and replace them with 2 Black drives and then striping them all giving me 1 large 8TB Volume made up of 4 x Western Digital Blacks.

    I was going to then use the 5 Western Digital Greens in an external enclosure and set them up as Raid 5. This way I have 8TB + a spare drive in case of any failures.

    I purchased a thinking that this would be perfect. But today I have found out that I am now slowing my system down using this method as its software raid and getting an enclosure which has Hardware Raid is a much better solution.

    The company I purchased the enclosure from now are asking for a 20% restock charge as the fault was that off my own.

    Is it worth sending back the enclosure and getting the Lian Li?
  2. -hh macrumors 68030


    Jul 17, 2001
    NJ Highlands, Earth
    Frankly, I don't like the idea of a RAID 0 stripe for a data backup drive. Ever.

    Yup, that would fix that RAID 0 problem.

    I'd not get too worked up about it. Afterall, the speed hit is going to be obvious on just the intial pass; a drive's speed doesn't really matter all that much after that, since most access will generally be done in the background and not huge.

    The main thing to keep in mind is that you've learned something for next time. Of course, if it really bothers you, then pay for the restock & repurchase.

  3. Tazdaman, Jun 27, 2012
    Last edited: Jun 27, 2012

    Tazdaman thread starter macrumors newbie

    Jun 17, 2007
    I am just trying to find a way to make the most of a bad situation and trying to understand what I should do.

    Would this work?
  4. nanofrog macrumors G4

    May 6, 2008
    Not very reliable, and gets worse the more drives in the set (i.e. 4 member stripe set is 4x more likely to die than a member run as a single disk).

    So if you don't have the time to fix the array when something goes wrong (fix the hardware, then restore data from backup + re-perform any work that was done between the latest backup and the RAID 0 failure), then this isn't the way to go.

    This is a good way to go, but you'd be better off using a redundant level for your primary storage.

    Which if you intend to do a level 5, means a proper hardware RAID controller card, and enterprise grade disks (consumer drives do not work with these cards due to the firmware timings are incorrect for the application). This results in such a solution being on the expensive side vs. what you've been looking at ($3 - 5k isn't uncommon for a modest configuration :eek:).

    At least you seem to realize that a software RAID 5 implementation isn't the way to go. :)

    But on the cheap (using the MP's SATA ports), it will do a RAID 10, and will work with consumer disks. You just have less capacity (smallest disk's capacity * 1/2 of n members = usable capacity). So with 8TB of raw storage via 4 disks, you'd get 4TB of usable capacity (2TB * .5 * 4 = 4TB ).

    Now you can get more than 4 members using your existing enclosure (one you've been considering returning), but due to the PM chip, it's going to slow things down considerably vs. a separate port per disk.

    There are cards and enclosures (not traditional SATA ports, but use MiniSAS connectors transferring the SATA protocol) that will do this far cheaper than a full blown RAID card that will result in higher throughputs (as a result of 1x port per disk, and cheaper due to the non-RAID cards can be had a bit cheaper + cheaper consumer grade disks <disks are where the real savings is derived>).

    I'm not seeing information that this includes a RoC, which is what the type of enclosure you're looking for will need (inexpensive hardware that will do RAID 5). The Qx4 sold by OWC is such an enclosure (does have an RoC <RAID on a Chip>).

    The compromise however, is they're not that fast or robust regarding recovery (still use a singe eSATA port to access all drives).

    As per a backup, you can use the same type of enclosure you're currently using, and create a Spanned set (concatenated, which appears as a single volume built from multiple members). No capacity loss this way either.

    Not as easy to rebuild in the event of a failure, but as this is a backup, you'd be fine (keep in mind, it's not very likely that both the primary and backup systems will go simultaneously; still possible, such as a fire or major natural disaster for example, but the % is small).

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