We have a pair of Netapp FAS2220-2 filers with the DS shelves. We have never had any reallocation scheduling setup and our partner has not configured this from day 1, we are now over a year since install and suffering performance issues. I have read up about reallocation, read-reallocation, space optimization, extent etc but i`m not 100% sure what the best practises are. I`m also not sure about wether to reallocate on a deduplicated volume or not. Some of our volumes are deduplicated and some are not (those with exchange db and SQL db).... What`s the best way to handle this? I have ran some measures on the volumes, some are showing as high as 8 with hotspots.
What i`d like to understand is what schedule should i perform on all of my volumes and should i be reallocating on deduplicated volumes as well? Additionally any advise on reallocate read / space optimization / extent would also be appreciated.
3.4 Free Space Reallocate and Read Reallocate When enabling free space reallocation on an aggregate, also consider enabling read reallocate space_optimized for the volumes in the aggregate. The two are complementary technologies that help maintain optimal layout. Read reallocate will optimize the system for sequential reads on the fly, while free space reallocate will optimize for writes.
Reallocation helps in two case - it optimized data layout (reduces fragmentation) and optimize sequential workload.
The former is inherent problem of any redirect-on-write filesystem. The latter depends on your use case, although in most cases you always have some sequential workload (even if you use snapshots for backup, you probably want to verify them and that does sequential scan).
De duplication unfortunately convicts with reallocation. Reallocation aligns blocks belonging to the same file, but decuplicYrd blocks may belong to multiple files, so which one should win? You still may want to use free space reallocation to optimize raid layout though.