Change disks with mirror-help

[Ayman Altounji]

We have a ML530 with two arrays. Array A (Raid 0) has one 18,2GB ScsiUltra3 10K disk. Array B (Raid 5) has six 18,2GB ScsiUltra3 10K disks. Now we have bought another two 18,2GB ScsiUltra3 with 15K speed. We want Array A to be Raid 1 and use the last disk as a hot-spare for both arrays.

Since the "old"-disks is 10K and the new ones 15K I thought it would be best that both disks in Array A (Raid 1) where exactly equal (15K that is) and use the rest for Array B and hot-spare.

I have created a mirror on Array A with the old 10K and a new 15K disk. Now I want two remove the old 10K disk from the mirror and then remirror the 15K disk with the other 15K disk. I want to do this when the server is running and without loss of any data. Is this possible and how?

Best regards
Bent Lund

[Ayman Altounji]

If you have a RAID 1 situation, you can replace a harddrive online.

[Ayman Altounji]

Thanks for your response.

Could you please tell me how this is done?

Thanks, Bent Lund

[Ayman Altounji]

If you have a mirrored situation (RAID 1), then it's possible to remove the defective hard disk (in your case the 10.000 rpm drive) on-line.

when you put the new drive (15.000 rpm drive) in the same drive bay where you just removed the old drive, the rebuild process takes automatically place until the mirrored situation is synchronized.

[Ayman Altounji]

Actually - I don't think you can do this... not without data loss. Reason being, you have absolutely no redundancy on the first array (one drive). You can't remove that one drive and replace it with a 15K drive and "rebuild" as there is nothing to rebuild from...

This radical of a change will require a complete reconfiguration to do.

[Ayman Altounji]

I'm not a RAID expert, but I think RAID 1 (Mirror) means that the two disks are equal and if one fails you will still be running with the other. Then you can replace the defective disk on-line and the mirror will rebuild.

I want to do this when both disks are running k. The documentation says you should not remove a running disk. So I thought I could use Array-manager to remove the first disk in the mirror from the array (go back to RAID nothing). Then I could replace the disk and create a new mirror. I just can't find the right way to do this without getting data loss.

The best way is probably to down the server, remove the first disk, re start server and then insert the new disk which will be rebuild automatically.

Any more thoughts?

Bent fund

[Ayman Altounji]

I think I misunderstand the situation right now.

Bent Lund wrote that he has already created a RAID 1 situation on array A with a 10k and a 15k drive, obviously with valid data.
In this situation (that I wrote above) , and basically in every RAID 1 environment with a SMART controller, you can replace one drive on-line with another drive (15k drive). Rebuild takes place from the other drive in the RAID 1.
Compaq recommends that you should not remove a "running" drive, but the SMART controller can of course handle it. (I think that Compaq does not recommend this because the array looses it's fault tolerance for a while) When you remove a running drive, you simulate a defective drive. Rebuild takes place if you insert a drive back in the bay. This can even be the same drive that you've just pulled out.
In addition: you can do this replace action off-line, when the server is down.

Again, this is true for a normal and running RAID 1 situation. As I wrote above I don't think I understand the situation Bent Lund wrote completely because in first instance there is a RAID 0 with one drive of 18GB. Later on he has "created" a RAID 1 situation, probably via migration from RAID 0 to RAID 1.