I've just added 10 additonal disks into an exisitng aggregate. The aggregate contains NFS datastores which in turn contain live VMDK files. The NetApp volumes containing the NFS datstores are deduplicated.
Do I reallocate or not? If yes, which command do I use?
We often have customers run a perfstat, or we run statit separately (perfstat contains statit) and statit will show disk utilization percentage. If mostly writes, you will see the new disks have heavier utilization but see how much.... if 50% or less it usually isn't an issue.
measure_layout is also a good method like Eugene mentioned, but statit may give what you need much quicker, or you can run both. For stati, "priv set advanced ; statit -b" wait a while for a representative sample of the counters then "priv set advanced ; statit -enr" and you will see util% on all disks. Check the disks in your aggregate and see the range of % between disks. For example if you see 10 disks at 95% and the rest at 20% it might make sense to reallocate....but if you see those 10 disks at 40% and the other disks at 20% it wouldn't.
Scott, good point about the statit command. I've checked util% and its running at 5% for the original disks and 1% for the new disks I've added.
I've seen the reallocate man pages, however I raised the question because of some other posts that I've seen. One guy says don't reallocate on a volume which contains live virtual machines. Is there any truth in that comment?
Just for clarity, the measure_layout increments range between 1 (optimised) to 10 (very unpotimised)? I get '2' for all volumes in the aggregate.
I realize this thread is older, but just FYI: The NetApp recommendation is to never run reallocate on deduplicated volumes. The deduplication process itself eliminates the benefits of reallocation and vice versa.
4.4 Deduplication and Compression Starting in Data ONTAP 8.1 deduplicated data can be reallocated using physical reallocation or read_realloc space_optimized. Although data may be shared by multiple files when deduplicated, reallocate uses an intelligent algorithm to only reallocate the data the first time a shared block is encountered. Prior versions of Data ONTAP do not support reallocation of deduplicated data and will skip any deduplicated data encountered. Compressed data will not be reallocated by reallocate or read reallocate, and it is not recommended to run reallocate on compressed volumes.