multiple disk sizes / speeds

[Suzanne_20]

I have an EVA8000 with 134 - 146GB 10kb drives configured into one disk group.

I now have 24 300GB drives to add into the SAN to increase storage.

The longterm goal is to be removing 146s to allocate to other sans.

Question: I was told that if I add the 300s to the 146 disk group, only 146GB of each would be available until all are 300s. is this true?

Currently, I have placed them all into their own disk group and began cloning some luns over there.

Is my information correct? Please offer advices, clarifications, etc.

Thanks,
Suz

[Amar_Joshi]

Suz,

This issue has been discussed many times in this forum. The information you have is wrong. You can alway mix up the different sizes in the same diskgroup and it will add up the exact same space to the diskgroup. But you need to be careful about the sparing capacity. In a mixed sizes diskgroup (in your case 146 and 300GB) the spare capacity is calculated based on the disksize of highest capacity disk in that disk group. In your case you will be reserving 2 times of 300 GB for single protection (or 4 times in double protection).

In my view it's always recommended to have different diskgroups for each size of disk (it possible) but not restricted to.

My 2 cents worth... still search in this forum.

[Rob Leadbeater]

Hi Suz,

As Amardeep says, what you have been told is wrong. You just have to be careful about the amount of reserved space defined by the sparing level.

Depending on your situation you may want to consider adding the 300GB drives to the existing group. The performance of a disk group increases as the number of disks in it goes up, so your new group consisting of just the 300GB drives may not perform as well as your existing group.

I assume you're also aware that your new group will be significantly smaller than the existing one...

Hope this helps,

Regards,

Rob