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Resizing PERC5i array, RAID5

Posted on 2011-10-10
Medium Priority
Last Modified: 2012-05-12
Our PowerEdge 2950 is nearly out of space. Currently there are three SAS drives, each 160ish GB in a RAID 5 array. What are my options? I've thought about adding a 4th disk to the array (if possible) or even ghosting the image and then replacing all three drives with bigger ones, if that would even work to begin with. Thanks!
Question by:TechGuy_007

Expert Comment

ID: 36945043
With a hardware RAID 5 array, I'm almost positive there is no way to increase the number of disks in the array (without destroying and recreating it). You could replace each drive in the array with a larger drive one at a time (letting the array rebuild before replacing the next drive). This would give you unused space where you could setup another virtual drive (assuming your RAID controller allows this). This would be seen to your OS as another hard drive, so you would either have to move some of your data to this new drive or use some sort of software RAID option (Windows has dynamic disks that you can use to do this) to span your original drive and your new drive to create a larger drive. I've done this in Windows (I actually added a 2nd physical drive to a server, but it's the same principal), but it does complicate things a bit. If you can afford the down time, you could ghost your current drive (or use some other backup solution), replace the drives, create a new array with the new drives, then restore the image/backup to the new array.

If you have the space to create a backup of your current array and can afford the down-time, I would go with the backup/replace drives/restore option.

Hope this helps.

Accepted Solution

kiwistag earned 2000 total points
ID: 36945760
If you can add a 4th disk in there should be an option to extend the array onto it. It may take several hours to do. Once this process is finished you should then be able to expand the Logical Drive on that Array.
After that you'll need to extend the partition on the Logical Disk to fill up (gPartEd is great for this).

We have done it several times with HP controllers. It is possible to do it (on HP) so that you install larger disks but you have to wait for each replacement disk to rebuild completely before doing the next disk in the series. This may take you days.. From there follow the above hopefully.
LVL 56

Expert Comment

by:Handy Holder
ID: 36947693
I don't know what this means but it might help...

"go to OMSA, Storage, PERC, Virtual Disks, choose Reconfigure from the dropdown menu for your RAID 5, follow the wizard to add the disk." (OMSA = openmanage server administrator)

Note Dell controllers aren't as flexible as HP ones, you can't add disks to a container that has two logical disks on it and you can't replace small disks with larger ones. Also generically be aware that you may be limited by the OS, for example you can't expand a windows MBR disk past 2TB although there is 3rd party software that will convert it to MBR without data loss that you can buy.


Expert Comment

ID: 36947738
Thanks andyalder. I didn't think they would be.
TechGuy_007: As per above try that. Unfortunately each RAID manufacturer has their own tools and limitations. Most should have the ability to expand the Array and if the OSMA allows it it's probably the only (easy) way to go.

Expert Comment

ID: 36948981
With this controller, there should be no issue adding a drive to a raid 5. If this was a multi-level array(raid 10, 50), I would recommend against it even though it is supported. As just a raid 5, there shouldn't be an issue.

If that is not enough space, then your thought about imaging would be the better way to add larger drives. Get a good image. Test it. Swap all the drives and make your new larger raid. Slap the image on and go.

I would HIGHLY recommend NOT rebuilding in a larger drive 1 at a time for more space. First, doing three forced fails with three rebuilds is three chances to have major failures. Second, if you splice a second array onto the same physical disks, a lot of wacky things can happen to a raid array. I have personally seen setups like this work great for years and never be an issue. I have also personally seen these work great for years until a drive fails and then lose both arrays. It is recommended for just about any raid controller to only have one array on any given physical disk.

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