topic Adding Disk to RAID 5 array online in Disk Enclosures

Adding Disk to RAID 5 array online

Romanek — Fri, 12 Jan 2007 17:23:04 GMT

I have a DL380 G4 with a SmartArray 6i controller. We are using 72 gig disks. I am going to be extending the array and the logical disk online. I understand that an addition of this size will take roughly 18 hours to extend the array, and then another 18 hours to extend the logical drive.

Does anyone have any data as to what kind of a performance impact I can expect during the array/logical disk extension?

Also, if this is done offline, will this increase the speed of the extension? If I can reduce the amount time this will take I may be able to get downtime, but there is currently no way this server can be down for 36 hours. Any information anyone might have will be greatly appreciated.

Thanks,

Blaine

Re: Adding Disk to RAID 5 array online

Matt Burgess — Wed, 17 Jan 2007 20:42:42 GMT

Hi Blaine,

This is the way I would do it:

Get either:

pci-based array controller

or

a write-back cache for the 6i

You do't need to buy these. You can use one from another server temporarily or (I've seen this done) order a replacement one and then send it back and tell HP you mis-diagnosed the problem.

Now that you have your cache, the migration process will complete in a fraction of the time. I would say < 3 hours.

If you can't do it that way you're going to have to bite the bullet and wait the 18-36 hours.

One last point - doing the extension off-line will ONLY be quicker if you have LOW expansion priority (which would mean that under load i/o would be given priority). I have tested this and KNOW it to be true.