topic Re: Thin Provision Volume and Lun? in ONTAP Discussions

Thin Provision Volume and Lun?

amgenung23 — Thu, 05 Jun 2025 07:26:17 GMT

It is possible to set the volume garantee to NONE, and then thin provision the LUNS within that volume? I would like to do this in hopes of having the aggregate benefit from the thin povisioning.

Possible? if so, Pros/Cons?

I suspect I will want to turn on auto-grow, to cover the storage. No Snaps needed so factional and snap reserve will be set to 0%.

Thank you,

Andy

Re: Thin Provision Volume and Lun?

radek_kubka — Tue, 30 Jun 2009 20:40:10 GMT

Hi,

It's a bit hairy topic.

First of all, be warned that no matter how you do your thin provisioning, you have to keep a close eye on your space consumption!

It is possible to set the volume garantee to NONE, and then thin provision the LUNS within that volume? I would like to do this in hopes of having the aggregate benefit from the thin povisioning.

Yes, it is possible, but not necesarily the best way to go forward. The gotcha is if you set vol guarantee to none, fractional reserve will be automatically set to 100% & there is no way to change it. You've said snaps are not needed. That's fine, but IF a single snapshot is created, then fractional reserve automatically kicks in booking that much space, as your LUN has used (not the nominal size of the LUN).

Interestingly enough, enabling A-SIS de-dupe on that volume will have the same end result, even if you have no snapshots at all.

How about creating space-reserved volume of a size to just fit your LUNs day 1 data (plus some common sense margin), thin provisioned LUNs & setting volume to auto-size? This will allow you to set fractional reserve to 0% and acheive the same and goal, i.e. save some space within aggregate due to thin provisioning.

Regards,
Radek

Re: Thin Provision Volume and Lun?

amiller_1 — Wed, 01 Jul 2009 00:14:44 GMT

You definitely can do this but I'd 1) be sure not to over-provision too aggressively (in a VMware environment at least, NFS removes some of the need for thin provisioning) and 2) definitely use Operations Manager and customize the alert values very carefully.