Adding disks to an EVA-4400

[Chris_at_MPM]

I wish to add storage to my EVA-4400 which is currently configured with eight 146 GB drives.  I have two questions about how to accomplish this:

1)  Can I add larger capacity disks (300 GB) to the enclosure and existing Disk Group?

2)  Once new disks are recognized by SAN, can I simply move them from the Ungrouped Disks group to the Default Disk Group that is being used now.

Thanks for any insight.

[Ivan Lyanguzov]

Chris,

The answer for both of your questions is — yes, you can do that. However I would highly recommend to first read a very good white paper with best practices for EVAx400 arrays configuration:

http://bizsupport1.austin.hp.com/bizsupport/TechSupport/Document.jsp?lang=en&cc=us&taskId=120&prodSeriesId=3900918&prodTypeId=12169&objectID=c02288914

Specifically, keep in mind that when you add a larger disk to a group of smaller disks, EVA puts more data on it, hence requiring more IOPS from larger disk. So, if you plan to replace all disks in a group with larger disks, it is okay to temporarily live with this, but if you want to buy just a couple of larger disks, they can become hot spots of your array.

HP also proposes a technical service — EVA Health Check — where configuration of your array is compared to best practices, and recommendations to configuration improvements are provided. I would recommend this service to be performed before installing new disks into array.

Ivan.

[hvhari]

It will be better to have larger disks in a separate disk group. White paper refered in the previous post will give you good idea on why this is recommended.

[Johan Guldmyr]

Also if you at the moment have let's say 90% used space on each 146GB disk, you will have 90% also on the 300GB disks.

This part about the 300GB disk being overutilized stands true, but it's not as bad if you for example would have added 600GB disks.

If you cannot get another disk shelf / enough 300GB disks to get a new disk group or for whatever reason, I'd suggest getting 300GB 15k drives, especially if the 146GB are 10k you should not suffer so much performance wise. Something you may want to check: Do you have a lot of IOPS now?

[rbanse]

We're in the same boat. We're going to be adding 6 - 600gb disks to our default disk group, which has 30 disks in it now. So this will expand the 1 disk group to 36 disks. Our PDS consultant said this is fine to do, and we would not lose as much space if we did it this way compared to created a new disk group. The disks in this existing group are 400 and 450gb disks at 10k and 15k.

[Torsten.]

In a new disk group you need to have at least 8 disks. While adding larger disks to a existing disk group, the system reserves the x-times space of the largest disk (single or double protection level), so you might have less space after adding "some" larger disks.