https://www-secure.symantec.com/connect/forums/sata-drives-usb-dock-be2012-whats-best-method-setup#comment-7068281

BE recognises each disks by their unique diskids.  Under some circumstances, two disk can have the same disk ids.  This will present a problem when they are used for B2D folders.  Below is how to fix this problem

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All our external USB SATA backup drives are recognized as normal Disk storage and I managed to add most of these to Backup Exec 2012 and put them in a Device Pool. Some disks from the same manufacturer batch were recognized as the same disk in BE Storage (e.g. disk 10 and 11 both showed up as disk 10) and I was not able to add a new disk device.

Then I thought what does maybe distinguise one disk from the other, the Disk Signature ID in sector 0. This is where Mark Russinovich, our SysInternals guru came to the rescue, because I found this article:http://blogs.technet.com/b/markrussinovich/archive/2011/11/08/3463572.aspx.

Work-around:

  1. Attach first disk to your server and use DISKPART to find the signature
    SELECT DISK #, where # is the disk number in you system (use Disk Management to find disk number).
    UNIQUEID DISK
    This will give you a 4 byte disk ID e.g. “e9eb3aa5”
  2. Now attach the second (or third, etc) and do the same, find the UNIQUE ID, which will show as the same ID as the first. With the same DISKPART tool you can overwrite the ID with a new ID, try incrementing the number with 1 (that is what I did) for each new disk.
    Use the command in DISKPART: UNIQUEID DISK ID=e9eb3aa6, where the ID is the id you choose, this is just an example (see also the article above).
  3. After the ID is changed, I deleted all BE folders from that disk (/BEControl and /BEdata), disconnect the USB drive and reconnected it.
  4. This time BE Storage does not find the disk in the list and you can Add a new disk.