Increrasing disk capacity in a RAID 1+0 and RAID 5 setup

[Ajitabh Pandey]

Hi,

I have some around 10 HP ML370 and DL585s. They are all configured either as RAID 1+0 or RAID 5+ADG systems. Some of the arrays are using 72GB disks, I have to upgrade the disks to 146GB. If I just remove the mirror disk and replace it with 146 GB, wait till the sync happens and then replace the primary disk with 146GB and wait till the sync happens. Is their a way I can make the RAID array utilise the full 146GB. Please also note that the system is RHEL AS3 with disks under the control of LVM with ext3 FS.

Any help will be appreciated.

[Steven E. Protter]

Shalom,

If these are two disk systems, pulling out a drive will likely halt them.

If they are raid 5 hardware, your procedure can work, one disk at a time.

If your raid setup is software pulling a disk will likely halt the system. If there is spare capacity in the servers, you pull off a rolling upgrade by adding disk, increasing volume groups and moving the data to the new disks.

This is however a wee bit risky.

Best bet is to use ghost or http://www.mondorescue.org or http://www.acronis.com to image the systems. then you should be able to bring them down, replace the disks and restore your systems.

If there are databases on the disk, the database or other transaction applications must be shut at backup time to get a clean backup.

acronis is the closest thing I've seen on Linux to Ignite which could handle this task easily if these were hp-ux servers.

SEP

[Ajitabh Pandey]

I will try to be a bit clearer this time:

The RAID on the disks are hardware RAID and all the disks are connected to either Smart Array 5300 (internal) or Smart Array 6400 (external) controllers. I have tw0 physical arrays configured as:

Array A --> 1 72 GB disk --> 1 72 GB disk (RAID 1+0)

Array B --> 2 72 GB disks --> 2 72 GB disks (RAID 1+0)

Array A has one logical drive and Array B has 2 logical drives. Further I have LVM configured on the RedHat Linux.

The objective I have is to change these 72GB disks into 146GB disks. I had the following theoretical plan which I am not sure will work.

Step 1. Replace the mirror pair of both arrays to 146GB disks so the layout is now as follows:

Array A --> 1 72 GB disk --> 1 146 GB disk (RAID 1+0)

Array B --> 2 72 GB disks --> 2 146 GB disks (RAID 1+0)

Wait for the sync to happen.

Step 2. Replace the primary disk with 146GB disks so the layout now is:

Array A --> 1 146 GB disk --> 1 146 GB disk (RAID 1+0)

Array B --> 2 146 GB disks --> 2 146 GB disks (RAID 1+0)

Wait for the sync to happen.

After these two steps I am still utilising the first 72GB of each disk as the array was created like that.

How can I extend the array to utilise the full 146GB disks? Will I see the new space as unutilised space? If yes then should I proceed as follows:

Step 3. Create new logical drives in each array.

Step 4. Reboot the machine (is it reqired?)

Step 5. Create a new physical volume. How? Will I see a new /dev/cciss/cxdx kind of drive?

Step 6. Extend the Volume group(s) to the new physical volume. I hope it is just the standard vgextend command.

Step 7. Extend the Logical volume(s) on the Volume Groups. Should be the standard lvextend command?

Step 8. Extend the filesystem on the logical volumes. I have ext3 filesystems. How to extend them? Can they be extended on the fly or shall I unmount the filesystem.

I am more concerned and want to double check steps because these are all production systems and I do not have a spare system to try the sequence first. Ofcourse I will take a backup first and will do that on the development system first, but still the app developers would love to have as low downtime as possible.

Cheers.