Reallocate can take a long time. You can increase the wafl scan speed which controls how much data is read and processed, but that can start to effect performance. I've not seen it effect performance to terribly, with out modifying the wafl scan speed. Naturally on workloads that are more disk intensive your milage may vary. 7 offers the ability to schedule regular reallocates to help with hot disk issues. Keep in mind new data will be written to the new disks, so as long as you add disks in groups, you shouldn't have too poor an effect on performance.
-Blake
On 4/11/07, Philip Boyle philip.boyle@eircom.net wrote:
Hi guys,
Has anyone seen any issues with using the reallocate command in relation to a) increase in snap shot usage b) performance impact c) length of time to run the reallocation?
I may have a requirement to reduce the raid group size option( currently 28 ) on an existing 12 disk aggregate to 16 and add additional disks, thus potentially creating the presence of 'hot disks' in the primary raid group which will have been increased from 12 to 16 disks.
http://now.netapp.com/NOW/knowledge/ docs/ontap/rel70rc/html/ontap/cmdref/man1/na_reallocate.1.htm
Any feedback on past experience would be useful.
I'm running ONTAP 7.0.4 on an FAS940 cluster with legacy LRC modules and 36G disks.
Thanks, Philip