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Thread: Expandable RAID / JBOD

  1. #1
    Join Date
    May 2004
    Up North
    213 times in 138 posts

    Expandable RAID / JBOD

    My storage server has 4 disks 400gb

    Currently this gives 4 drive letters, I`d like to merge this into one, but here's the problem:

    I want to be able to add a drive to the array, and transparently increase the size.

    Can any JBOD implementations do this?

    Redundancy (RAID1/5) isn't an issue as its dvd images/ tivo shows.

    Ideally I'd also like to be able to clear a single disk (if there is enough free space on the array) and remove it. (That would be similar to a parition resize in ghost...)

    Is this all asking too much in 2006 ?

    The only answers I seem to find are to build another large array, then copy from one to another, and throw the old one away.

  2. #2
    Senior Member
    Join Date
    Sep 2005
    7 times in 7 posts
    You can't dynamically modify your array with software RAID, meaning, if you have the drives plugged into the little SATA jacks on your motherboard, you can't do it. By RAID, I also mean JBOD.

    You need a RAID add-on card. The very best one on the market IMO is this one. I bought the 4-port version twice. It runs in one of the graphics card PCI-Express x8/16 lanes on modern motherboards, rather than a regular PCI slot.

    The reason you need a add-on card is because only basic features are provided with software RAID, but with a good hardware RAID card, you will be able to have up to RAID-5/6 (something that software doesn't usually allow), meaning parity information is stored on 1/xth of your system's total space (where x is the number of drives in the array). This means that any one drive can fail without losing any data or even causing any down-time. A good RAID card will simply allow you to whip out the bad drive, and insert another, and it will instantly rebuild.

    Another RAID card feature is Array Migration, where if your RAID card dies, you can take the drives and put them into another RAID card from the same company (or at least one that follows standards) and plug them in, in any order, without losing any data.

    Dynamic Array Expansion and RAID-type adjustment means that if you want to add another drive, it will be added to your existing RAID volume automatically, without any disruption to your existing data. In addition, a GOOD RAID card won't just add the extra capacity to the end of the array, but will rearrange all the parity data so it's spread even over all the drives. In addition, it will give you the option of upgrading your RAID type at the same time (i.e.: switching from RAID-0 to RAID-5 to RAID-6, etc.).

    With RAID, there is no ability to "clear" one drive so it can be removed like you stated in your question. Instead, you would simply pull it out, and allow the RAID-5 / RAID-6 parity features to keep the array operational (it's HIGHLY recoomended that you immediatly put a new drive in the empty slot). If you pull one disk out with the intention of using it for something else, you would have to reformat it at it's destination.

    Now, here's the catch. Windows needs a little help to expand the partition when you have the RAID card expand the volume. It can only expand SLAVE (non MASTER) volumes, meaning that Windows cannot be installed on the volume that wou want to expand. Your SLAVE volume must also be formatted as a "Dynamic" drive (vs. a "Basic" drive) so that it can be changed in the future when you are ready to add drives to your array.

    First you will need to use the driver CD with the RAID card to install the card itself so Windows recognizes it. Then you need to go into Disk Management and "import" the disk. Assign it a drive letter, and there you go.

    First of all, don't even think about using a RAID array that you plan of upgrading, expanding as a MASTER volume to install Windows. For that, just use a single drive (you're not storing much info on the MASTER anyway), or if you REALLY want to RAID your MASTER, either RAID it through crappy software RAID (on the motherboard jacks), or RAID it on a SEPARATE array on the RAID card from your SLAVE array.

    Reason is: if your software RAID controller craps out (like they frequently do), all you have to do is reformat/reinstall Windows... you have not lost any files b/c you keep your files on a SLAVE. But the REAL reason is if you plan on upgrading your array, Windows WILL NOT allow you to modify the MASTER partition. So, you might have added a ton of extra drive space to the volume, but Windows will not change it's partition size. The extra space, you could turn into another parition, but that would defeat your purpose b/c (1) you are getting another "drive" letter, which is the reason you are asking this question, and (2) now, you are storing data on a MASTER array, so if you have to reformat Windows, you lose all that data, EVEN if it's on a different partition.
    Last edited by latrosicarius; 08-04-2006 at 07:07 PM.

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