adding drive to raid 5

Although the actual method of adding a drive will depend on whether you have a software or hardware RAID implementation, the drive will become part of the existing array if you so desginate it to be. Raid 5, as a "standard," will allow up to a maximum of 32 drives in a single array (if I remember correctly). You can have multiple, independant arrays. Or you can mirror arrays (sometimes as RAID 50 (RAID 5 + Raid 0)).

With a hardware implementation, all RAID implementations are supported. You are limited to using SCSI and to a single array per SCSI channel. Although you can use drives of different sizes , you are wasting any space over and above the size of the smallest drive.

With a software implementation (such as is found in WinNT4 and Win2K), you are limited to RAID levels 0, 1, or 5. Because the implmentation is partition-based (vs. drive-based), you can mix and match drive sizes as well as drive types (IDE or SCSI) and not waste space.

Hope this clears up some confusion.

Assuming hardware RAID, when you add a drive (install it physically, that is), to an array controller, it initially appears as a single drive not part of any array. Then, you use the drive controller's BIOS or software installed under your operating system to configure the array. At this point, you can make it part of the same array either as a spare or as a regular member of the array. If you are using software RAID under NT or Win2K, you would install the drive physically and then go into NT Disk Administrator (or Win2K Computer Management Console) and add the drive to the array from there. You cannot make a single drive into a separate array, since you need a minimum of 3 hard drives to configure a RAID5 array. Hope this helps!

Tim & "Synergy" are quite right. Unfortunately, they don't quite answer the question (as I see it, at least).
As mentioned, if this is a hardware RAID, you should be able (depending on the RAID controller) to join the new physical drive to the existing array, which means that from now on all the data will be distributed among all the drives, including the new one. However, a second problem to this solution lies in the OS since that (assuming NT4/W2K) will not allow you to "stretch" your logical drive to include the new one. Intead, what you'll have to do is create another logical drive using Disk Administrator and possibly chain it (create a "volume stripe") to the existing drive to create a larger logical drive. This will allow you to use a single drive letter (partition) for all your data and have you protected as far as the RAID protection goes.
on our tests, at my workplace, we have come to the conclusion, however, that it might prove more beneficial to backup all the data, recreate a new raid array using all the drives, and then restore. This way there's no reliance on the OS to manage any logical drives (which can [and has] prove fatal at times), and you also have a much "cleaner" environment, possibly leading to better performance as well.

Hope this one helps too.
Gal.

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This question was closed by the author