Expand RAID 5 logical

Posted on 2006-05-25
Medium Priority
Last Modified: 2010-04-27
Proliant ML570 with one full drive cage, one logical volume with data. Second drive cage has 2 drives (mirrored)/one logical with OS. Can I add drives to the 2nd drive cage and expand the logical drive on on the first array/ cage. Please respond with array controller options only. We don' t want to do this in the OS.
thanks in advance
Question by:Derf238
LVL 18

Expert Comment

by:Don S.
ID: 16764487
Are both cages driven from the same smart array controller?
If yes, then you should be able to do it.  If no, then probably not.

Expert Comment

ID: 16764820
Are you using the onboard raid or to you have a separate RAID controller?

Expert Comment

ID: 16764873
For onboard here is the RAID management software that will allow you to reconfigure the array without loosing data.

windows 2003

windows 2000
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LVL 44

Expert Comment

ID: 16766808
You have given inadequate information to assess what you have.  But here is probably a correct estimate.  The 2 drives in cage 2 are a RAID 1 mirror for the OS partition only -- RAID 1 mirror for security, to avoid losing the OS.  THe answer is, you cannot expand this array.  2 drives are the maximum -- you can increase the size of BOTH at the same time, but you cannot enlarge one at a time, the capacity will remain the same as the smallest drive.

The 3 drives in cage 1 are a RAID 5 array of 3 drives, the RAID 5 is supposed to be more reliable and better speed than the RAID 1, but this is not the case with reliability.  You should immediately get a drive 6, and go into the RAID bios and attach the new drive you have to the RAID 5 array.  Make it a FAILOVER DRIVE, for the RAID 5 array, not part of the array.  The reason is, if one drive in that RAID 5 array fails, you might be able to recover the array, but if 2 fail, you cannot.  However, if you have a 4th drive readied by the RAID controller to susbtitute for the first failed drive, then you are reasonably safe.  

You can enlarge the RAID 5 array by adding drives,  however, the system is limited to 6 drives, so with one failover drive, you are maxed out on the system.  Therefore, you can only realistically enlarge the drive capacity.  In this case, you will have to buy ALL bigger drives at the same time, copy all the data off to a different drive (like an IDE larger capacity, replace all the 3 RAID 5 drives, and then copy the data back into the larger array.  ALWAYS keep a failover drive available for a RAID 5 array.  If a drive ever fails, you will be happy you did, if not, you could lose all the data.

Author Comment

ID: 16772641
scrathcyboy - let me rephrase as I'm not sure you fully understood the question.
there are 2 drive cages in the server. The first cage has 2 drives. As you stated, this is a mirror set w/ the OS. There are no other drives in this cage at this time. The second cage is full. It has 6 drives in a RAID5 configuration as a data volume. The question is, without digressing to a discussion on failover drives, can I put additional drives in the empty slots on cage 1 to expand the drivespace on the array in cage 2.

Accepted Solution

thur6165 earned 2000 total points
ID: 16772735
Scrathy completly missed the question, and it wont be the last.  Anyway, this is more than possible, use the utility above after you put the drives in so that you don't have to reboot.
LVL 44

Expert Comment

ID: 16773083
I did not miss the question, I got it perfectly, you and the other respondent dont seem to realize I already answered it.

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