Internal RAID5 ..?

Discussion in 'Mac Pro' started by -hh, Aug 7, 2012.

  1. -hh macrumors 68020


    Jul 17, 2001
    NJ Highlands, Earth
    Now that I've completed my basic setup of my 2012 Mac Pro, I'm looking at it from the perspective of what is its weak links, and what I'm presently keyed in on is that the Time Machine backup isn't very huge (only 2TB) and it is on a single spindle.

    Current configuration is:

    Optical Bay#1 - OEM Superdrive
    Optical Bay#2 - empty
    3.5" HDD Bay1 - OEM 1TB (bootable)
    3.5" HDD Bay2 - Data; disk1 of RAID-0
    3.5" HDD Bay3 - Data; disk2 of RAID-0
    3.5" HDD Bay4 - Time Machine
    PCIe Slot/Accelsior SSD - System boot drive

    My thoughts are that I can pull what's in HDD Bays 1 & 4 and also put a tray into Optical Bay#2 to put in three new/identical 3.5" HDDs to create a RAID5 for having some reliability for my Time Machine backup.

    Question is...

    (a) would this work?
    (b) what is needed?

    For (a), my concern is that the SATA channel for the Optical Bays may not necessarily be "identical" to the four standard 3.5" Bays ... is this a real concern?

    For (b), I know that Disk Utility only supports RAID1 & RAID0 .. not RAID5, so I would either need a 3rd party application to create a RAID5, or I'd need a PCIe hardware card from which to then run cables. If I would have to go the latter route, it raises the question of if a DX4 bracket and four 2.5" drives might be a viable alternative.

    I do recognize that I could go with an external like a Mercury Elite Pro box, but I'd like to explore the internal options first.

    Comments, Suggestions?

  2. JavaTheHut macrumors 6502


    Aug 15, 2010
    This seems like a decent use of the spare Optical bay-- if you went with a raid card
  3. nanofrog macrumors G4

    May 6, 2008
    You'd be better off putting the RAID 5 up for primary data (improved up-time due to redundancy, as well as additional throughput if your applications can take advantage of it), and placing your Time Machine volume externally (i.e. eSATA card + Port Multiplier based enclosure kit). You'd have the option of configuring the drives in the enclosure as single disks, JBOD, or 10 (I recommend avoiding a RAID 0 for backup like the proverbial Plague).

    As per using a software implementation for RAID 5, I cannot stress enough DO NOT DO THIS, as it cannot address the write hole issue associated with parity based arrays. So you'd need to use a proper hardware RAID controller card in order to deal with this (solution to this issue = hardware).

    Now with a hardware based RAID 5, another thing to consider is the drives used. Consumer grade drives will not work due to their firmware is not properly compatible with RAID controllers (has to do with the recovery timings programmed into the drive's firmware). So you'd have to use Enterprise grade HDD's, which are more expensive. Worth it though, as they'll work as expected, and tend to last longer anyway (better specifications oriented to a RAID environment, as well as firmware designed to work with hardware RAID controllers).

    As per how to configure this in a 2012 MP using internal drives, there is an adapter that would be needed (here).

    Another method, would to be use the linked 2.5" HDD backplane cage, and the correct cable (here).
  4. pprior macrumors 65816

    Aug 1, 2007
    Listen to nanofrog.

    I've got most of my data on a raid-6 external box and it backs up over the network to a raid-5 time machine drive, but time machine itself seems to be far more likely to lose data than the drive. I've had to twice basically reformat my time machine drive because time machine won't recognize the current backup sets there, even though the drive is available and working fine. Not super impressed with TM.
  5. goodcow macrumors 6502a

    Aug 4, 2007
    You could also use the new Western Digital Red line, cheaper than their Enterprise (RE) line, but designed for SoHo NAS.
  6. hfg macrumors 68040


    Dec 1, 2006
    Cedar Rapids, IA. USA
    My system is on an older 2008 MacPro and is configured such:

    Bay1: 256GB SSD Boot / Applications (OS X and Windows)
    Bay2: 1TB RAID-0 slice for OS X data
    Bay3: 1TB RAID-0 slice for OS X data
    Bay4: 500GB oem disk for Windows data

    OWC RAID-5 Mercury Elite Pro Qx2 on dual eSATA card for TM backup
    DROBO FS NAS in the basement on ethernet for TM backup

    Both of the external drives are mounted in Time Machine and it alternates backup between the two backup systems each hour.

    (I am not real happy with the DROBO FS speed however, but once the initial backup was done, the incremental backups are tolerable. I would hope to restore from the OWC if needed, but having the remote extra copy is comforting).

    I did find nanofrog's suggestion interesting and it got me thinking about having the RAID drive redundancy on my primary data, and a simpler drive (RAID-1?) for backup.

    I would not put my backup in the same enclosure as my primary data. A simple power supply failure could take them all out at once.

    How do you like your OWC RAID-0 PCIe Slot/Accelsior SSD? I have been looking at that recently.

  7. VideoFreek macrumors 6502


    May 12, 2007
    Interesting, I would have steered clear of RAID 5 for primary data due to performance you see read/write speeds close to RAID 0 performance in a RAID 5 array?
  8. cutterman macrumors regular

    Apr 27, 2010
    I think you are better off avoiding 3rd party storage options for time machine. In those cases where you need to install drivers to mount the volume, you won't be able to do a system restore from your backup using the install disk or recovery partition.
  9. nanofrog macrumors G4

    May 6, 2008
    I'd want to test them out first, as I recall that WD's NASware is necessary in order for them to work properly, which lends me to believe they're software array oriented (most off-the-shelf NAS systems are software based, not hardware), rather than true hardware RAID controllers. Wording is a bit ambiguous IMHO, so I'm cautious (seen similar wording before with storage products from various manufacturers that turned out to be software based rather than hardware).

    Now assuming they will be compatible with a proper hardware controller (potential users would need to wait for their card maker to test them out or buy a few and test themselves), their throughputs seem to be aimed at backup/archival duty (slightly faster than the Green variants). So not the right disk series for performance is critical applications.

    Hence the mention of the enterprise HDD versions only.

    I'd skip Time Machine all together, and use a 3rd party software package with whatever storage system that will accommodate the capacity.

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