Restoring Domain Controller on to new Raid

May 16, 2010 at 11:54:18
Specs: Server 2003 R2 Standard
I currently have our main fileserver and Domain Controller running a Raid 1, two drives. I would like to change this to a Raid 5 with 4 or 5 disks. The Client pcs are all XP Pro and logon to the DC. I will need to format the server to configure the Raid 5 but dont want to have to visit each client to log them onto the domain again. Is there any easy way to retsore the server so it's all back as it was just on Raid 5? I will have a full backup of the C: partition including system state.

Many Thanks


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#1
May 17, 2010 at 07:52:10
When I did my server, I simply disk imaged the system on an External Drive then made not of the partition tables. I formatted the drives (was upgrading to 8 drives) then setup the partition so that I had the same number (the data partition was now larger) and restored the image back.

This was a backup DC but the same principle should apply. Worst case you have to rebuild you Domain and rejoin the computers if it fails. I have step by step instructions written down for rebuilding my domain as part of our disaster recovery plan. I assume you have the same.
(With this being the worst case your manager may not appreciate the down time.)

The best option is if you have a spare server that you can experiment with that has the same hardware in it then I would try it on that box before going live.

P.S. Look at it this way you can now test your backup plan to make sure you can do a restore in the case of a system failure.


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#2
May 17, 2010 at 08:54:58
You would need a product like Acronis to image your existing system. You would initialize the new raid array but you would never format it. Replacing the image back on the drive also includes the base file system which is why formatting isn't required.

Restoring the image will put things back the way there were concerning AD and the workstations.

moblies
I would add that going to a raid 5 array IS NOT A GOOD IDEA. It is a long standing standard in the industry you mirror the OS and raid that data. By keeping the OS and Data separate if one or the other fails you only have HALF the risk/problem getting the server back online. Having the data separate also allows you to do a backup, increase the disk array size and then restore. Again half the risk and half the problem

I would recommend instead of raid5 you bring up another mirror set and move all of your data/shares to this array.

You should also have a hot spare in your raid array for dynamic drive failover. This will save you considerable downtime/loss of productivity since it will allow you to schedule when you replace the failed drive or just reinit a new hot spare.

This means you need three drives not just one.


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#3
May 17, 2010 at 12:36:03
Thanks for the info guys, The server is our main File server / Domain Controller, in terms of data we have porbably about 45gb on the mirrored drive. It's Dell PE2900 and with the embedded raid a Perc 5i I think - Will it allow me to add two more drives to create a mirror for the data without affecting the original mirror with The OS on it?

To be fair I have had Raid 1 for the last 10 years and never had any problems , likewise I have had some Raid 5 and usualy had a disk go.

Thanks


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#4
May 17, 2010 at 13:03:43
according to your server specs
"Standard internal hard drive bays support up to eight 3.5" SAS or SATA hot plug hard drives"

from here:
http://www.dell.com/us/en/dfb/serve...

There is never a problem with any raid controller to make multiple raid arrays. It's all a matter of having the disks and how you team them.

45gig is a lot to make an image of. Might want to consider having a good tested backup of the data and then delete the data before you do the drive image. Under these circumstances I would consider pulling the shadow drive from the system, replace it with a new drive and remirror. If all fails you still have the shadow drive to boot up on


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#5
May 18, 2010 at 12:43:09
Sounds like a Plan, downside is looking at the cost of the drives, server is nearly 4 years old and will be replaced at some point so not sure if i'll gain anything. Raid 1 has served me well for the amount of data we store is it worth it? Redundancy between them seems to be the same. Have had a few people commenting on how it should have been Raid 5 instead of 1.

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#6
May 18, 2010 at 13:22:37
raid5 is slower imo than raid1. In raid1 you can read from both disks different data at the same time. It just lags due to dual writes.

Looking ahead you will apprieciate having your data on a separate volume set.

The whole raid5 thing with two partitions sucks when it comes to upgrading or dealing with OS issues.


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#7
May 19, 2010 at 08:07:08
RAID 5 has the best of Both worlds. It only costs one drives worth of spare for the parity bit and it takes advantage of striping to give you speed. RAID 0 you have all speed no redundancy and RAID 1 you have redundancy at the cost of 1/2 your disk space. If you really want speed and redundancy you may want to look into RAID 1+0 but it is more expensive so most go with RAID 5.

"The whole raid5 thing with two partitions sucks when it comes to upgrading or dealing with OS issues."

That only depends on if you are doing a software RAID or a firmware RAID. I like firmware RAIDs but the big problem with them is if the controller fails then you are screwed. You have to get the exact same controller when fixing it.


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#8
May 19, 2010 at 08:32:27
Raid 0 speed, by itself, is a urban myth. I have personally tested this for gaming and data on many different controllers.

Cost of a drive(s) compared to the advantages has never been an issue for me. Data redundancy has always been worth the cost.

Though Raid 0+1 is good Raid 10 is better for both speed and failover. Both use 4 drives minimum. I use Raid 10 or 1 for my databases. Which I use depends on volume and the number of users accessing the database.

Concerning using Raid 5 and upgrading/troubleshooting I think you missed my point.
For example lets say you want to add a disk to expand your OS partition. Lets also assume your raid controller can do dynamic stripping on the fly. Once complete you have your original partitions plus extra space at the end. You can not add it to the OS partition without removing the data partition and then using third party software to expand the OS partition.

Compare this operation to having separate arrays for OS and Data. It is easy to backup, expand and restore the OS array.


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