Multiple external drives and RAID

Discussion in 'Mac Basics and Help' started by principii, Oct 24, 2008.

  1. principii macrumors newbie

    Joined:
    Oct 24, 2008
    #1
    Hello - I am kind of new to this, so please forgive me if I am vague!

    I have two hard drives that already have my music on one and my videos/images on the other. I want to use them as external drives for my mac.

    I would like to use this particular dual-bay case, which comes with RAID capabilities. I know that RAID is used to force the multiple drives to be used as one drive but I actually want to keep the drives separate, but just in the same case.

    Could anyone here please tell me if it is possible with an enclosure that CAN do RAID to choose NOT to use RAID?

    It is this case: http://www.epowermac.com.au/shop/pc/SATA-Xpress-RAID-Case-Only-355p704.htm#details

    Overall, this case is the one I like best in terms of looks and it's both within my price range and in my country (Australia) so I don't have to cough up for postage from the US or some other far away place. It took me ages to find one I was happy with so I would really prefer not to have to find another one.

    Thank you all for any advice you can offer.
     
  2. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #2
    Well, it says it supports JBOD, but that can be either just concatenating all drives together or, as some mfr's do, means no RAID at all (aka separate drives). I'd call the manufacturer and ask.
     
  3. blodwyn macrumors 65816

    Joined:
    Jul 28, 2004
    Location:
    Portland, Oregon
    #3
    The reference to RAID 0 is the concatenation option. The JBOD setting would allow for both drives to be used separately and independently
     
  4. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #4
    RAID 0 is not simple concatenation of drives. The manufacturer says it supports JBOD or RAID 0. JBOD can be either concatenation or single disks, and that depends on the manufacturer's definition. RAID 0, is nowhere close to being similar to JBOD. RAID 0 stripes the data across the disks.
     
  5. blodwyn macrumors 65816

    Joined:
    Jul 28, 2004
    Location:
    Portland, Oregon
    #5
    From Wikipedia:

    A RAID 0 (also known as a stripe set or striped volume) splits data evenly across two or more disks (striped) with no parity information for redundancy.

    JBOD stands for Just a Bunch Of Disks (Just a Box Of Drives).

    I agree with the striping, although concatenation is what the end result looks like. But JBOD's are *not* concatenated within the box. A JBOD *can* be used to construct a RAID 0 array by using software or a controller external to the box, but as far as the box goes, it's just a bunch of un-concatenated disks.
     
  6. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #6
    Well, if you're going trust Wikipedia, you might as well visit here:

    http://en.wikipedia.org/wiki/Standard_RAID_levels

    I know what JBOD stands for, and it doesn't necessarily mean it will show up as separate disks. The array controllers I have used will setup JBOD as no striping and just concatenating one disk after the other. I have no idea what this particular unit does; I have never seen JBOD present as separate disks, but the one the OP pointed out may do that.

    RAID 0 may "appear" as concatenation, but it is not an accurate description of how it works. Additionally, JBOD can combine various size disks and come up with the sum total of the sizes, whereas RAID 0 will not.

    By the way, where did you get that last acronym? I've always heard it as "Just a Bunch of Drives" for the past 15 years.
     
  7. blodwyn macrumors 65816

    Joined:
    Jul 28, 2004
    Location:
    Portland, Oregon
    #7
    I got the definitions from the same page you linked to - the JBOD acronym is towards the bottom of that page. I'm most familiar with the term "Just a Bunch of Disks" going back to the original Clariion days where I think I heard it first.

    I've never heard of a JBOD that's been anything other than (by definition) just a bunch of disks as far as the appliance is concerned, i.e. no concatenation done within the unit, but from Googling around it looks like you're right, which kind of goes against the term JBOD IMHO.

    I've always seen the appliance present the disks individually. For example at home I have a 4 bay enclosure with 4 disks in it, configured as a JBOD, so each disk is presented individually. I have configured 3 of them into a ZFS RAIDZ volume, but I'm doing that with software external to the box, not within the box itself.
     
  8. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #8
    You all have to stop arguing about the fine points of some definition. These boxes are made in Chine by people who don't speak English. The printing on the outside of the box is likely written by a non-native speaker with no or little experience in the subject.

    The only way to know what it really does is to read the user manual. In some cases even the manual is unclear.

    I've even seen the term "RAID" used to describe a simple mechanical enclosure that had no controller inside. Many times it's marketing people who write these things.

    My opinion is that JBOD is "just a box or disks" but we have no "acronym police" and I can use the term of mean "John's But's On the Deck." to refer to a guy named john setting on a pier fishing.
     
  9. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #9
    Interesting.... last Clariion I worked on was a FC4700. What a slow, slow beast, at least in comparison to today's systems.

    I haven't played with ZFS at all, especially since we stopped using Sun for anything these days. How do you like it?
     
  10. belvdr macrumors 603

    Joined:
    Aug 15, 2005
    #10
    Good grief, the other person and I were just discussing things (not arguing), and we both learned some things from it, so what's the harm? At least, I wasn't upset by any of the comments. If it bothers you that much (at least your post came across that way), then why not just ignore it?
     
  11. blodwyn macrumors 65816

    Joined:
    Jul 28, 2004
    Location:
    Portland, Oregon
    #11
    I set up my RAIDZ array several months ago using version zfs-111 from macosforge, and have upgraded to each new version. I've had no issues whatsoever with it so far, although I stay away from the known problem areas - like ejecting the volume using the Finder which causes a kernel panic. It took about 2 minutes to set up, and has just worked ever since.

    It's pretty slow, as my enclosure is USB2, so all the data is going through one USB cable. I consider this a torture test setup and so far it hasn't skipped a beat, but I'm not using it as my primary data storage while it's still in development so I don't care about the performance right now, although I'd be curious how it performs at SATA speeds. I'm looking ahead to when Snow Leopard ships and will probably migrate my main data storage over to it if/when I get a Nehalem Mac Pro.
     

Share This Page