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Extending array size

Eric Shupe
Occasional Contributor

Extending array size

I have an HP A-500 Server running 11.0. There is a SC-10 drive array connected via a 4Si controller. The SC-10 currently has 3 18GB drives in it setup with RAID5 giving me about 36GB total storage, all in one Volume Group(vg02). I have a new 18GB drive to add to the array that I want to use to create a new Volume Group with a size of about 18GB to load some new software on. Now from what I have found the only way to do this is to delete everything that is on the array, put the new drive in, and then recreate the array. Then I would need to recreate my vg02 and restore the data back to it and then make a new Volume Group and load my new software. Is this really the only way to do it?? Adding disk space should not be this hard! Please give me any advice you may have.

Honored Contributor

Re: Extending array size

Hi Eric

Once cannot enjoy best of both worlds , RAID 5 gives you a redundancey interms of a disk failure , so essentailly waht aheppend is that the system treats a disk as a parity disk for the other two and there is a complex alogrithm which works for this combo , now to add another disk you need to recreate this combination so that the reduncdancy can be still maintained in teh array .

Manoj Srivastava
Sean OB_1
Honored Contributor

Re: Extending array size

Unfortunately you are correct. The issue is raid 5.

Raid 5 stripes data across 2 of your 3 disks and uses the third as a parity disk.

To add another disk to the array you need to recreate the raid group.

A different option would be to replace the existing 18G disks with larger disks.

Then you wouldn't have to recreate the entire raid group.

Leif Halvarsson_2
Honored Contributor

Re: Extending array size

What you can do is up to the Raid controller, some controllers has more advanced features then other (and are more expensive). As I can find the 4Si supports hot swap disks and multiple Raid sets. At least it should be possible to add more disks and create a new Raid set (and then use it for a new volume group). Yes you MUST create a new Raid set if you want to create a new volume group. What perhaps is not possible without recreating is to add a drive to a existing Raid set. Another question, not clear to me, is if it is possible (with this controller) to create a Raid set with only one disk (and no Raid security). As I understand you have only one extra disk.