Increase disk size on RAID5

Question

I have a 1600 with raid5 using 3 9gig scis hard drives.  I am running out of room.  Has anyone tried to install larger hard drives, ie, 18 gigs each or more.  If i get 3 larger hard drives and install them one at a time, letting the raid rebuild each time, will this enable be to end up with a larger overall usable space when the last one goes it?  If not, will it work if I replace all of the and then take out one and put in another of the same size?

warwizard55 · Answer

Hi Techlaision

Well that first method would get you an 18 GB RAID 5 with 8 GB or so unused on each drive. Dell does not recommend creating a second RAID array in the unused space... Assume you do so, then on array 1 disk 1 goes off line, and on array 2 disk 2 is offline... you have to add a 4 th drive to rebuild one of the arrays before you can replace any drives. Very difficult and time consuming to fix.

How about this... add 1 of the 18 GB drives and make it a RAID 0 with 18 GB, then use disk management to mirror your 18 GB RAID 5 to it. Once the data transfer to the mirror is complete, you can break the mirror, go into the management utility and reconfigure or transform type to be a 3 drive RAID 5, by adding the other two 18 GB drives. you'll still have the original partition sizes, but will have an additional 18 GB your D: can be expanded to use.

warwizard DCSP

techliaison · Answer

Well the many times I have done Raid5 and replace bad hard drives, I know you can put a bigger hard drive in, it just will only use the amount of disk space the other smaller hard drives.  Why would it not work if you replace the existing small hard drives with bigger ones.  That is replace one, let the data rebuild then replace another and continue the process until the larger hard drives are in place.  Would this allow for expansion of the data drive after it is done?

RGPJR · Answer

Hi, I'm on the forum now trying to get the answer myself. I have done this in the past a few times and I believe I was able to. I just am unsure now because I'm trying to do it again and I'm running into issues.   I am speaking about removing and installing larger drives in PE systems with RAID 5 while they are running. For instance, I have a PE2550 with 146GB drives that I just replaced with 300 GB drives. You simply remove one drive at a time and wait until the rebuild is complete on the new drive. After all the drives are replaced, you will notice the unallocated space in the Array Manager console. In the past I have successfully 'reconfigured' the Virtual Disks to utilize the unallocated space. I know it worked in the past, because the only other way to extend the container would be to destroy it and re-create it. I'm in the situation now where I am doing just that in this example.   I have other servers now in the same situation: larger drives in place and unsuccessful attempts at increasing the container size.   I'm basically trying to find out the truth to this method.

warwizard55 · Answer

Hi RPG JR,

Well I was just in a 3 day lab class and have been dealing with the Dell Servers for 7 years, most of the tools that dell provides do not have the ability to change a 3 drive RAID 5 with 300 GB, into a 3 drive RAID 5 with 600GB. All the array manager tools let you add drives as the method of adding space to the RAID 5. As I stated above the usual method of replacing 1 drive at a time then creating a second logical drive in the unused space is no longer recommended due to problems recovering from drive faults.

I pointed out one method of getting around it, that works in the special case where you are doubling the space in a 3 drive raid 5, for the ones going from x sized to 4x, or 8x larger drives, the best practice will be to back up your data, review the backup logs for any files that were unable to be backed up, fix the files as needed till you have a good backup, then replace the drives, (retaining the old set as a backout plan), and create your new array, reinstall the O/S and restore from your backup. I fully understand that down time conciderations may preclude this approach, and you will have to piggyback the logical drives. A hot spare or open slot may be essential for recovery should your two arrays each develop single faults on two different drives, as replacing either drive that is single faulted introduces a unrecoverable double fault in the other array unless it's already been rebuilt to the hotspare.

warwizard DCSP

P.S. A 5 drive RAID 5 may be mirrored to a 4x sized drive, and a 9 drive RAID 5 can be mirrored to a x8 sized drive.

techliaison · Answer

Thanks, i appreciate the advice.  Just wonder and had never tried, saves me a lot of time on testing.

RGPJR · Answer

HI Warwizard,   You are correct - once the containers are created and no more drives can be added to the array, you need to destroy and restore. I find that it is easiest to to leave the boot container available and the OS running while destroying and restoring the other container(s). Especially if the system is an ADC controller or other mission critical system that is unless you need the boot container's size increased. I too have been working on Dell servers now for 6 plus years- I love em! Thanks for the advice!

tcdrake · Answer

I have a PowerEdge 6600 with RAID 5. I want to add to more drives to my RAID, these drives are the exact same size and model as the rest of the RAID. How do I configure the ARRAY so these drives are part of it?

warwizard55 · Answer

Hi TCDrake,

Sorry I nearly missed your post, I was going thru the old notifications on my dashboard, and found this.

Do you still need assistance? The procedures have been posted many many times in this forum, you should be able to do a search and come up with a half dozen posts giving procedures for which ever O/S, controller, and management tools you are using.

warwizard DCSP

tcdrake · Answer

Thanks but already taken care of. Since this was my first go at it I just called Dell Tech Support and they walked me through the configuration after I added the drive.

PowerEdge HDD/SCSI/RAID

Increase disk size on RAID5

Was this post helpful?