HI I have a Proliant ML150G2 with 4 160Gb drives in a hardware raid 5. (it is our main domain controller – we do have a backup domain controller) The array have been split into 3 so the c (system) partition is part of the raid 5. Not ideal I know, it was already setup when I got here. I want to get a mirror of the system partition (c Drive). What is the best way? Can I just add another dive and then use windows disk manager to mirror c: Will it work if I attach an external hard drive and then use windows disk manager to mirror c: Fairly new to RAID so not sure what the best method is – I don’t want to start from scratch Many Thnaks

"I don’t want to start from scratch" but you would have to if you wanted to change the raid level. "Can I just add another dive and then use windows disk manager to mirror c:?" Technically speaking yes you could software mirror. This is where you need to educated yourself to the difference between hardware raid and software raid. Here is what you need to understand: 1. you lose two disks in your 3 disk raid5 you lost everything and you are only as good as your last backup. Google Hot Spare 2. if you software mirror the OS partition to another drive if you lost the raid5 array you lost everything except the OS [no data only os - back to #1] 3. if you lost the OS partition [and its boot] on the raid5 array you should be able to boot to the mirror and still access your data IF the OS sees the original OS as gone. If the partition is still there but not mountable it will be assigned a drive letter and you will not be able to mount your server programs or access data via the original drive letters. No real failover here which makes this a waste of time and resources. Now if you used a server version of cloning software you could clone the OS partition to a drive and then mirror that drive via the hardware. Then you could repartition the raid5 array and restore from backup so the drive letters/partitions all matched before the change [so everything works]. You would need two additional drives to accomplish this. This is not a technique for someone new to raid or hardware configurations. Imagine the power of knowing how to internet search http://www.lib.berkeley.edu/Teachin...

Kind of pointless to mirror a raid array with a single disk. Not to mention the performance hit when trying to use a software raid. The way you mirror a 5 go higher with the hardware adapter. See the adapter docs for building a raid level you wish above 5. A daily ntbackup would be better in my opinion. I have never had a raid 5 fail (not a config change but a failure) to the point I have had to rebuild it. We have lost controllers, backplanes, fans and even a few drives at once. I read it wrong and answer it wrong too. So get off my case you peanut.

"The way you mirror a 5 go higher with the hardware adapter." jefro is referring to raid 50 which increases performance not fault tolerance http://www.acnc.com/04_01_50.html "A daily ntbackup would be better in my opinion" Raid protects you from hardware failures and keeps you operational. Backup doesn't do that for you but it is the next step in a recovery plan. "I have never had a raid 5 fail (not a config change but a failure) to the point I have had to rebuild it. We have lost controllers, backplanes, fans and even a few drives at once." If you lost two drives you had to rebuild the array. Sure are a lot of posts on the internet concerning raid array failures. Another reason to have hot spares configured in the array!!!! Imagine the power if you knew how to internet search

I don't know why you resort to insults in every discussion that remotely disagree's with your position. The OP needs to read his doc's. He may have the ability to improve the array. We have a lot of system from mylex to smartarrays. All have good feature that can sometimes be used hot. Yes, we normally run mylex's with 5 disks, 3 hot, 2 spare. You can loose two disks. I read it wrong and answer it wrong too. So get off my case you peanut.

Insults jefro? All I did was clarify information you alluded to but were not specific about. It would appear you were not clear on the differences between what raid provides and what backup provides. They are very different yet you made it seem like they were equal or provided the same service. At times jefro I don't think you really understand what the issue is that needs to be addressed. For example your comment about the Mylex raid controllers. The OP wants to mirror the OS, which presently resides on a partition, without redoing the raid array. So how do you propose to do that given the Mylex controller? Can you hardware raid a partition on a raid5 array to another drive? Of course not because you can't hardware raid any partition only the drive or drives a partition can reside on top of. Now if you consider information correction/clarification to be insulting I truely do apologize. But in the best interests of the public and this forum I think it best that if anyone, myself included, posts information that is vague, incomplete, or can lead to a misunderstanding on the part of the OP then its everyone's responsiblity to address the issue. Imagine the power if you knew how to internet search

"Yes, we normally run mylex's with 5 disks, 3 hot, 2 spare. You can loose two disks." I read your "you can lose two disks" as saying you can substain the loss of two disks in a raid5 array which isn't correct. Now you wouldn't want the public to think you could lose two disks in a raid5 array and still remain viable would you jefro? Imagine the power if you knew how to internet search