How to change the size for HP smart array without losing data

Question

For a HA clustered setup (RHEL 5.8), my HP DL 380p G8 server consists of this:

mirrored root disk(RAID 1):

array A
physicaldrive 1I:2:1 (port 1I:box 2:bay 1, SAS, 300 GB, OK)
physicaldrive 1I:2:2 (port 1I:box 2:bay 2, SAS, 300 GB, OK)

a hot spare for the root disk:

array A
physicaldrive 1I:2:4 (port 1I:box 2:bay 4, SAS, 1 TB, OK, spare)

and a backup disk(RAID 0):

array B
physicaldrive 1I:2:3 (port 1I:box 2:bay 3, SAS, 300 GB, OK)

My questions are:

1. What's the function of hot spare ?
2. Does the 1TB space assigned to the hot spare means it won't be available physically?
3. I want to change the space for the backup array to 1-TB and change the size of the hot spare to 300 GB. Can this be done without losing any data ? (Note I already have my application running in `/apps` folder.

Answer 1

1.- The hot spare is a disk that its used by your controller when one of the disk of the RAID 1 fails. When that happens, it will kick automatically the hot spare disk so you won´t loose redundancy. Then you will have to replace the faulty disk and when that happens, the controller will automatically restore the raid to its original state and disable the hot spare disk.

2.- That´s right, you can´t use the 1TB space assigned to the Hot Spare.

3.- You can do this if you are using hardware raid. Be aware that you will lose all the data on the 300GB disk. You should backup the info on this disk first. After that, just reboot the server and boot it using the HP Smart Array CD. Using this app you can change the settings on the array. You should be able to assign the 300GB backup disk as Hot Spare for the Array A and then assign the 1TB disk to the Array B.

I suppose that it will be possible to do this on a software RAID but I can´t help you with that because I lack the knowledge.

Hope it helps! ;)