Hi Daniel,
On Tue, Jul 8, 2008 at 7:52 PM, Daniel Keisling < daniel.keisling@austin.ppdi.com> wrote:
Greetings,
I have a FAS3040 running 7.2.4 that is used primarily for LUNs over FCP. I balance most of the filesystems across four LUNs in two volumes groups spread across both controllers. I would like to add additional space, but was wondering if there were best practices in terms of buying two shelves at a time (like some other vendor's models) or if a single shelf is okay. Since I spread the space across both controllers, is it okay to distribute the disks on a single shelf to both controllers? Will this affect RGs or performance in any way?
The only best practice that I can think of that may apply here for a clustered configuration, is to always add more than 3 disks to a rg at one time, to prevent hotspots in your raid and thus performance loss.
Also, if you are running a configuration with syncmirror (such as a metrocluster), your configuration may be a bit more complex and you would have to split the disks not only over the heads, but also over the pools. In this configuration adding a single shelf usually results in low net space being added, since the disks are split 4 ways, resulting in 3 - 4 disks per rg, so I would recommend to add at least two shelves when expanding a metrocluster.
HTH & HAND
Nils.