Question to the Storage Advisors, from John: I have several large SCSI arrays ranging in size from 600 GB to almost 2 TB. They add up to about 4.5 TB in total. They are currently seen as separate drives in Windows 2003 server R2. I’d like to find an adapter card that will let me span them so they appear as one large array. I’d rather not span them using disk manager in Windows 2003.

John, first, are you willing to temporarily dump your data to tape in order to reconfigure the storage? This is probably a requirement because I’m not aware of any RAID controller that can combine multiple logical drives without losing data.

Next, are these SCSI arrays created by an external SCSI-to-SCSI controller that you plan to keep? If so, you need to make sure the logical drives are presented in a way that makes the drives look enough like a physical drive to be striped by your new PCI RAID card. You’re probably ok on this point. Also, are these logical drives presented by the SCSI-to-SCSI controller all the same size? If not, you’re going to have trouble striping them and using all of your capacity since each component of the RAID-0 has to be the same size. (In other words, the minor stripe size has to be the same on all drives.) You might end up creating one RAID-0 across all the logical drives, and then another across the “extra” sections of the logical drives, and so on. And of course you’ll have to have a RAID card that supports this; most of them don’t. (Hopefully I’m clear about this – if not, let me know and I can draw a picture.)

The easiest way to fix this is simply attach all your drives to a single PCI RAID card and create a single new array. Don’t bother trying to stripe the arrays that you currently have. Just start from scratch.

Feel free to drop more details about drive count and sizes and I can make a more concrete recommendation on how it can be configured. Also, have you already figured out what RAID type you need to use?

TT

This entry was posted on Friday, May 18th, 2007 and is filed under Storage Interconnects & RAID, Advisor - Tom Treadway. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.