RAID and Adding Drives

[mmaki]

I understand the concept behind RAID 5 (distributing parity) and how data can be restored if a drive fails and a new one is added, but here is my question on that concept: We have a new server with three 36GB SCSI drives (6 bays) and RAID controller. If I set it up with RAID 5 and later decide to add another 36GB drive, can I add the drive to the array? In other words I believe if I wanted to add the drive I had to reformat the array with the new drive or add the drive as a seperate partition.

Thanks!

Mike

 

[garcher]

The real answer is "It Depends" -- a lot of the higher end RAID controllers support an on-line expansion of the raid. Effectively what it will do is in the background restripe the data across the new drives even with activity (R/W) going on as well. Performance will SUCK while the restripe is going on as it has to move existing data and re-calculate parity.

If your RAID setup supports the concept of a "hot-spare" the odds are good that it will support dynamic expansiion.

 

[bozo1]

What garcher said. All depends on if the controller supports it.

Beyond that, once the expansion is complete, the extra space shows up as unpartitioned space. You either have to create a separate partition with the free space or use something like the server version of Partition Magic to add it to an existing partition if you wish.

 

[garcher]

<< What garcher said. All depends on if the controller supports it.

the extra space shows up as unpartitioned space. You either have to create a separate partition with the free space or use something like the server version of Partition Magic to add it to an existing partition if you wish. >>



Actually Microsoft has released a nice tool called DISKPART that works on W2K as well as WXP. This allows you to extend the partion of a basic disk as long as the free space appeared at the end of the partion. Microsoft as a Knowledge Base Article that describes how to do it (just ignore the cluster information).

Link to DISKPART Tool Download
Link to KB Article

 

[mmaki]

Thanks for all the great replies. I'll have to take a close look at the specs on the controller for this new server. It will be running Linux with Samba, so the MS stuff is of no use. Since we have a good reliable backup system, when the time comes we can add the new drives, format, reinstall the OS, and put the data back. Kind of a pain, but it's not like it is a mandatory 24/7 server, we can afford a day of down time.

Thanks again!