Hi all,

I'd like to pick your collective brains about your experiences with
reallocate, specifically when reallocating luns under VMware.

For background, we're running ONTAP 8.0.1 on a 3170 that's over three
years old.  I've been going through measuring reallocation, and most
of the volumes are over 3.  We have no snapshots, and only a
relatively small number of volumes are de-duplicated.  All our volumes
and luns are thin-provisioned, and no aggregate is more than 76% full
(most are ~65%).  We regularly have huge latency spikes (worst I've
seen so far is 5000000ms, and there are far too many to even track
over 50000ms daily), and on one filer head, but not its partner, I
regularly see disk utilisation go to 100% or more.  I'm hoping
reallocate will help here.

I have a brief note from a NetApp support person who says "It’s very
important that you complete the reallocation in the following order:
1:OS 2:LUN 3: Volume".

I have two questions about this:
 - is it absolutely necessary to defrag the OS before you reallocate
the lun?  I'm sure I've run reallocate without defraging the OS and
still seen performance improvements.  I'm also assuming that this is
only relevant to Windows VMs, not Linux (in our case, Red Hat/CentOS)
ones.
 - if you only have one lun per volume, do you still need to run
reallocate on both the lun and the volume?  If only one, which is
preferable?

All advice appreciated.

Thanks,
Peta

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