remove snapshot reservation

[TDUBB1234]

when i create a volume in a aggr. there is always 20% reserved for snapshots.

then afterwards I remove it

snap reserve -v vol_name 0

Is this set on the aggr level or I have to turn it off manually per volume?

aggr options my_aggr shows:

nosnap=off, raidtype=raid_dp, raidsize=16, ignore_inconsistent=off,

snapmirrored=off, resyncsnaptime=60, fs_size_fixed=off,

snapshot_autodelete=on, lost_write_protect=on, ha_policy=cfo

Is it bad to remove this 20% reservation?

[scottgelb]

The root volume is used as the default for new volumes.  "vol status" to see which volume is root.  That volume has the 20% reserve and is used for new volumes.  Most don't want 0% for root so need to modify new volumes after creation to have a different %.

[peter_lehmann]

It is not bad to set the snap reserve to 0%. It depends how you want to manage the space within the volume. I always set it to 0% for volumes with LUNs and NFS Datastores and SnapVault Destination data.

You are right, there is a snap reserve on the aggregate as well. Be careful,  when setting this to 0% you also "disable" the snapshots on aggregate level (because of snapshot autodelete)... And if you want to mirror the aggregate (with local_syncmirror) then you need the aggr snap reserve to be set to at least 5%. I very rarely change this to 0%.

Hope this helps,

Peter

[scottgelb]

The 8.1 default for the root aggregate will be 0% aggr reserve and I think the default for other aggrs will be 3 or 5% still (we'll know for sure when released hopefully at the end of the month). 

I don't like leaving it at zero either and had one case where we were able to aggr copy -s to copy a specific aggr snap to get a volume back that was deleted accidently at a customer.  I really wish we had "snap reserve -A -t file" to restore a flexvol as a single fle restore at the aggr level since it is an aggr object but that doesn't work today... aggr copy -s is a workaround but requires enough space and a full copy of that snap to get a volume back...but is a good use case on what we can do with aggr snaps even without syncmirror.

[aborzenkov]

aggr copy -s to copy a specific aggr snap to get a volume back

Excellent!