Mountain Lion JBOD questions

Discussion in 'Mac Accessories' started by nrajack, Apr 3, 2013.

  1. nrajack macrumors member

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    #1
    Been reading online about using Apple Disk Utility to create a JBOD array. Did some searching here and ran into something I need clarification on. Read here that one type of JBOD creates a set such that each drive is accessible separately and that there's another type of JBOD that creates one huge drive ala spanning. I'd like the former - each drive available separately to ML. Which version does Disk Utility do?

    The drive I'm looking at is the LaCie Little Big Drive 4 terabyte Thunderbolt drive. This one: http://www.lacie.com/us/products/product.htm?id=10573

    It has two separate drives.
     
  2. Giuly, Apr 3, 2013
    Last edited: Apr 3, 2013

    Giuly macrumors 68040

    Giuly

    #2
    The LaCie 2big always shows you two independent disks. It's preconfigured in a RAID0 for 2x the speed (which then shows up as a single disks), but you can just reformat them with Disk Utility like you'd do with any other hard drives.
     
  3. nrajack thread starter macrumors member

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    #3
    Help me to understand: if I take the stock from the factory RAID 0 setup, connect it to the computer and just reformat that with Disk Utility without making any changes in the RAID setup inside DU I'll see two separate drives on my desktop? This is in ML 10.8.2 on a mid-2011 27" iMac (should have mentioned this earlier) - sorry.
     
  4. Giuly macrumors 68040

    Giuly

    #4
    All the enclosure does is presenting two hard drives to the OS. However you end up formatting them is up to you.
    You can put two partitions on a RAID0, or you delete the RAID and format the disks individually.

    As far as I remember, you can even swap one hard drive for an SSD and turn it into a Fusion Drive on 10.8.3.
     
  5. nrajack thread starter macrumors member

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    #5
    The reason I'm a little concerned is the LaCie in question comes from LaCie already in RAID 0. Didn't know exactly where the actual RAID 0 'code' sat - drive(s), enclosure, or somewheres else. I guess I should be able to delete the RAID 0 setup from within OSX Disk Utility then, right? Go to the RAID tab? Just want to make sure before I screw it up.
     
  6. g4cube macrumors 6502a

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    #6
    You'd be hard pressed to screw it up.

    In Disk Utility you will see both the individual drives as well as the RAID-0 created volume.

    You can reformat, which eliminates the RAID volume, and then you just format each drive into a separate volume.

    In your original message, you were a bit confused by the name. The Little Big Disk is a different drive with either 2 HDD inside, or 2 SSD inside, all 2.5" drives.

    The link you posted is for the 2big, which has 2 7200RPM HDD inside.
     
  7. nrajack thread starter macrumors member

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    #7
    Thanks for the reply & info. I normally don't have problems doing relatively low-level stuff but dealing with RAID is new for me. I didn't know Disk Utility would eliminate the RAID volume on a reformat. The net is full of conflicting info on that - some people have posted no success with Disk Utility dumping the RAID for example. And looking at diskutil command line stuff looks like it could REALLY mess things up.

    Sorry for the confusion on the drives - my bad. :eek:
    I had different windows from LaCie open at the same time. The drive I'm talking about using is the one with the 2 7200 RPM physical platters (2big). I've been rethinking my drive setup here and wanted to do my research before I spent the cash. So many different drives and ways to go for externals it sometimes gets confusing.
     
  8. marzer macrumors 65816

    marzer

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    #8
    JBOD is a non-standardized term to describe a form of disk concatenation. OS X disk utility does concatenation or spanning. When you can access each drive in an enclosure separately, that's not JBOD, but simply referred to as independant drives.
     
  9. marzer macrumors 65816

    marzer

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    #9
    Yeah, I'd be concerned too about a multi disk enclosure being software RAID formatted out of the box. It's unusual for a manufacturer to software RAID format drives, its not typically considered transferrable. Under Windows or any other OS that out-of-box RAID 0 format is useless.

    But yes, because its software RAID dependant there's no RAID controller in the enclosure. You can reformat the drives anyway you please using disk utility without worry of screwing anything up. It'd the same as working with two internal SATA drives.
     
  10. nrajack thread starter macrumors member

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    #10
    As I said I'd read this info online and it seemed to conflict each other (there supposedly being two types of JBOD). Thanks for straightened this out.

    There's not a lot of explicit info on the LaCie site on what type of RAID system they use - hardware or software based. And they don't do tech support until you buy a drive. That's why I figured I'd ask here. The drive I'm looking at has easily user replaceable drives. Thanks much for the info. Just wish I didn't have to wait for the drive as the vendor I'm buying from appears to now be out-of-stock on these with more coming.
     
  11. marzer macrumors 65816

    marzer

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    #11
    For a multi independant drive enclosure, that looks like a nice option. Not many multi disk enclosures permit independant drive access. Or provide TB interface yet. I use the OWC Elite Pro specifically for the indepedant drive acces in one enclosure. But they've not upgraded it to TB yet. Though they do offer it in a TB package, including a Lacie TB hub.
     
  12. Giuly macrumors 68040

    Giuly

    #12
    LaCie doesn't use any kind of RAID system, it's just an enclosure for two separate disks, which means that there's no RAID chip to slow the operation down, and Intel's CPUs are so fast that the load introduced by the software RAID is insignificant (<1%).

    The RAID magic happens on OS X's Disk Utility. (Mirrored -> RAID1, Striped -> RAID0, Concatenated -> 'Spanning')
    [​IMG]
     
  13. nrajack thread starter macrumors member

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    #13
    I think I'm beginning to understand this. It would seem then that there being no RAID chip in the LaCie drive there would be a little bit of code on each individual drive in the enclosure that identifies it as a RAID member drive (slice) when seen by OSX?

    I've been using computers in one form or another since the 1970's (IBM punch cards) and RAID is a new area for me to actually use. I've known of RAID systems but never actually used or come into contact with one until now.

    Thanks all for sticking with me on this. I tend to get a little dense at times in my old age.
     
  14. marzer macrumors 65816

    marzer

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    #14
    A good RAID chipset does not slow operation down, it will maintain reliable throughout regardless of system load. Relying on the CPU (even current CPUs) via software implementation can slow down overall drive performance. Esp. when the system is subject to heavy loads. In industrial applications, software RAID is not even a consideration due to its lack of reliability and performance.

    And the OS X software RAID is not robust. I've tried it on and off over the years and have found it to be very error prone; on USB, FW800 and SATA interfaces. All three modes; 0, 1 and 1+0. Requiring frequent rebuilds or reformats.

    If someone needs RAID, first choice would be a reputable HW RAID solution. If your going to settle for software RAID for anything other than tinkering I'd strongly recommend a reputable third party solution.
     
  15. g4cube macrumors 6502a

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    #15
    Some alternate points to Marzer's comments:

    • MacDrive Pro from Mediafour is a driver for Windows which permits using Apple formatted drives on Windows 7 and 8. The original MacDrive only worked with single drive volumes. The Pro version adds support for OS X Disk Utility RAID volumes.
    • CPU performance of Sandy Bridge and Ivy Bridge processors as used in more recent Macs have plenty of CPU power, making the overhead for software RAID insignificant. As another poster noted, CPU utilization is quite low.
    • Actual HW RAID solutions are really dedicated, embedded processors. Like the main CPU in your Mac, the RAID solutions are implemented with code - firmware - that executes the algorithms that implement RAID. And even these dedicated HW RAID solutions do have overhead, as performance is a bit less than the sum of each individual drive performance.
    • With Apple's Disk Utility, information about drive members within an array is stored in partitions on each of the drive, so each drive knows where it belongs.
    • JBOD simply means "Just a Bunch Of Disks". There is no implication as to how they are formatted or used. As the OP noted, each can be individually formatted, partitioned, and used. Think of it as a multi-drive dock with a single connection to connect to your computer.
    • Apple has made a number of improvements to Disk Utility with each release of OS X, making it pretty robust. Of course, RAID-0 is used for performance, not fault-tolerance. RAID-1 is brute-force redundancy. It would be great if there were a software-based RAID-5 or RAID-6 solution. Some Linux releases have this.
    • SoftRAID is an alternative to Apple's Disk Utility for creating RAID-0 or RAID-1 arrays on OS X. It improves on Apple by adding more robust features of interest to end-users: http://www.softraid.com/features.html

    Let me conclude by saying that not everyone needs a RAID-0 or RAID-1 solution.

    Some use the multi-drive chassis as a drive dock with each drive simply formatted as a single volume. Various projects can be dedicated to a single drive, and the drive can act as a project archive. Easy addition of drives, and easy removal for storage makes for an efficient archiving solution. Since the drives are not protected by any cover, normal static-handling precautions should be followed.

    The multi-drive solutions provide a tool to some users that is a bit more convenient, and less expensive than the connection and cabling of multiple individual external drives. It is not an end all solution, just an alternative.
     
  16. Giuly macrumors 68040

    Giuly

  17. kapalua12 macrumors 6502

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    #17
    So in following this discussion I have a question about LaCie's 1 TB capacity Thunderbolt Little Big Disk SSD for roughly $999. I assume that the LaCie enclosure implements hardware raid
    out of the box? No software implementation or CPU overhead necessary?
     
  18. g4cube macrumors 6502a

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    #18
    Works out of the box.

    No HW controller

    2 separate 512GB SSD devices from Micron, striped in RAID-0 by Apple Disk Utility.

    Comes preformatted for the Mac OS X.

    Less than 1% CPU utilization.
     
  19. kapalua12 macrumors 6502

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    #19
    So if it had a hardware controller it would be better?

    Thanks.
     
  20. marzer macrumors 65816

    marzer

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    #20
    Yes a HW controller does provide a more reliable solution for RAID. As I indicated earlier it off-loads the CPU and ensures consistant throughput at all times even if the computer comes under heavy load. And from my hands on experience is far more reliable over time than the software RAID provided in OS X. However, if you don't have mission critical data and have a reliable backup plan it'll probably be sufficient as a personal storage solution.
     

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