topic Re: Aggregates free Spaces Checking in ONTAP Discussions

Aggregates free Spaces Checking

edlam2000 — Wed, 04 Jun 2025 13:28:19 GMT

May I know how & where to check if the Aggregate is running out of spaces, to avoid LUN offline because of not enough spaces to expand.

I have an Aggregate 16 TB with 6 TB used spaces as displayed in Web GUI.

However, when I checked its 3 x Volumes (with Dedup and Compression Storage Efficiency) which are all Thin Provisioned (total volume spaces over-provioned to 18 TB), all 3 x Volumes are 90% spaces utilized.

Inside the 3 x Volumes, all the LUN with Space Reservation but NO Snapshot.

This has led me to think that the Aggregate might be running out of disk spaces soon despite the Aggregate is still showing 6TB used spaces only.

How to check if my aggregate isn't running of spaces soon???

Re: Aggregates free Spaces Checking

aborzenkov — Mon, 30 Jul 2018 04:27:20 GMT

You do not say what ONTAP version you have; in current ONTAP LUN space reservation is honored only on thick provisioned volume (i.e. when space reservation is enabled for volume itself) which matches what you see.

Re: Aggregates free Spaces Checking

edlam2000 — Mon, 30 Jul 2018 07:13:00 GMT

My ONTAP is version 9.1P7.

My Volumes are Thin Provisioned and my LUN are space reservation enabled.

If LUN space reservation is only honored with Thick Volume, then I don't understand why my 16 TB aggregrate is only 6 TB used by my Thin Volume is showing 90% used.

Below is my GUI displayed:-

1) Only 6 TB used out of 16.67 TB (It has 3 Volumes inside)

2) From below you can see that my ONLY Thin Provisioned Volume 15 TB has 3.77 TB left.

I think it's due to that it only has 1 x 14 TB LUN (1 TB free) and dedup & Compression has saved 2.94 TB.

Re: Aggregates free Spaces Checking

edlam2000 — Mon, 30 Jul 2018 07:24:00 GMT

My ONTAP is version 9.1P7.

Below, you can see that my 16.67 TB Aggregate has 3 volumes with only the 15 TB volume is Thin Provisioned.

The 15 TB Volumes has 3.77 TB available because of following:-

1) There is only 1 x 14 TB LUN with Space Reservation Enabled leaving 1 TB volume spaces free

2) Dedup & compression has scheduled to run just last Monday morning (7 days ago) reported to have saved 2.93 TB volume spaces.

I don't understand how come my 16.67 TB Aggregate is reported to have only 6.37 TB used, while from the Volume level, it's only having 3.77 TB available.

Re: Aggregates free Spaces Checking

aborzenkov — Mon, 30 Jul 2018 10:09:37 GMT

Which is exactly why having thick LUN on thin volume is not recommended - it looks too confusing.

Logical volume space is indeed near to full due *logical* space reservation on volume level, but only actually consumed space is ever allocated on physical (aggregate) level.

Besides, as soon as you start using deduplication and compression it is impossible to tell exactly “how much space is left” even theoretically.

Re: Aggregates free Spaces Checking

SudheerAluri — Mon, 30 Jul 2018 10:25:15 GMT

It may be because of the fact that the 15TB volume is thin provisioned. Even if the LUN is created as thick, thin volume is reporting only actual utilization to the aggregate.

Re: Aggregates free Spaces Checking

edlam2000 — Tue, 31 Jul 2018 01:51:36 GMT

You mentioned about once using Dedup and compression, it's impossible to tell how much spaces is left, and that worry me.

I read from document that Dedup and Compression requires about 4% of volumes free spaces and 3% per volume for Aggregate free spaces.

Since I don't have any snapshot, I have not enabled spaces reservation.

I have left about 1TB free spaces for the Volume and the aggregate is still showing only 6 TB used.

How can I check to avoid LUN offline from insufficient spaces in Volume and/or Aggregate????

Re: Aggregates free Spaces Checking

SudheerAluri — Tue, 31 Jul 2018 03:44:47 GMT

I have left about 1TB free spaces for the Volume and the aggregate is still showing only 6 TB used.

6TB is the actual usage on the disk. when the utilization of luns increase aggr utilization also would report an increase. if you want to test place a big file in the lun and check the aggr utilization.

How can I check to avoid LUN offline from insufficient spaces in Volume and/or Aggregate????

If there are no new volumes get created on the aggr utilization should't go higher than the size of already created volumes.

Another way is to changes the space-guarntee of all 3 volumes to volume from none.So aggr free space should report free space than those volumes capacity.

vol modify -volume TEST -vserver testvserver -space-guarantee volume

Re: Aggregates free Spaces Checking

edlam2000 — Tue, 31 Jul 2018 04:13:46 GMT

Thanks, I worrying there could be insufficent spaces for the LUN because my LUN is 14 TB, with its containing Volume 15 TB which can autogrow/shrink to 16.5 TB, but since my aggregate is 16.67 TB, contains another fixed volume of 1 TB, the 2 x volumes together are already over-provisioned to 17.5 TB exceeding the aggregate size of 16.67 TB.

My last run of the Dedup&Compression on the 15 TB Volume that has just run last night (it runs weekly on Monday midnight) shows that total saving is 3.55 TB.

I just want to have a wy to check to make sure that the LUN won't go offline because either of insufficient volume spaces (which not likely to occur because I always leave about 1 TB free volume spaces), or insufficient Aggregate spaces.

Re: Aggregates free Spaces Checking

edlam2000 — Wed, 01 Aug 2018 01:26:37 GMT

How about if I change the LUN to Thin without Space Reservation????