topic Problem with agregate free space and snapmirroring in ONTAP Hardware

Problem with agregate free space and snapmirroring

PASCAL_78 — Thu, 05 Jun 2025 06:14:16 GMT

Hello everybody.

I've got 2 FAS 2220 with 8.1.1 7-mode.

I activated asynchronous snapmirroring (on nfs_logs) , and it's working fine, but I can see that agregate free space is going down.

The first time (before snapmirroring), the output was like it:

aggr show_space -h

Aggregate 'aggr0'

Total space WAFL reserve Snap reserve Usable space BSR NVLOG A-SIS Smtape

24TB 2479GB 0KB 21TB 0KB 0KB 0KB

Space allocated to volumes in the aggregate

Volume Allocated Used Guarantee

vol0 173GB 4258MB volume

nfs_logs 21TB 105MB volume

Aggregate Allocated Used Avail

Total space 21TB 4363MB 626GB

Snap reserve 0KB 0KB 0KB

WAFL reserve 2479GB 18GB 2460GB

Now :

aggr show_space -h

Aggregate 'aggr0'

Total space WAFL reserve Snap reserve Usable space BSR NVLOG A-SIS Smtape

24TB 2479GB 0KB 21TB 0KB 0KB 0KB

Space allocated to volumes in the aggregate

Volume Allocated Used Guarantee

vol0 173GB 4653MB volume

nfs_logs 21TB 8425MB volume

Aggregate Allocated Used Avail

Total space 21TB 12GB 614GB

Snap reserve 0KB 11GB 0KB

WAFL reserve 2479GB 18GB 2460GB

I dont't understand why snap reserve is growing, because agregate scheduling isn't working:

snap sched -A

Aggregate aggr0: 0 0 0

Thanks

Re: Problem with agregate free space and snapmirroring

LTDCLSERGAO — Fri, 07 Dec 2012 10:38:25 GMT

Hello,

Could you give ; df -Ah and snap list -A

Re: Problem with agregate free space and snapmirroring

PASCAL_78 — Fri, 07 Dec 2012 10:47:01 GMT

Hello Said, this is the output:

df -Ah

Aggregate total used avail capacity

aggr0 21TB 21TB 614GB 97%

aggr0/.snapshot 0GB 11GB 0GB ---%

and :

snap list -A

Aggregate aggr0

working...

%/used %/total date name

---------- ---------- ------------ --------

17% (17%) 0% ( 0%) Nov 30 09:00 hourly.0

20% ( 4%) 0% ( 0%) Nov 30 00:00 nightly.0

22% ( 4%) 0% ( 0%) Nov 29 19:00 hourly.1

25% ( 3%) 0% ( 0%) Nov 29 14:00 hourly.2

27% ( 4%) 0% ( 0%) Nov 29 09:00 hourly.3

Re: Problem with agregate free space and snapmirroring

LTDCLSERGAO — Fri, 07 Dec 2012 11:11:33 GMT

strange !!!!

Could you verify the date at which you disabled the aggragat snap sched ?

Is there any script taking this snap ?

If no , delete this snap and observe what is going to take place.

Re: Problem with agregate free space and snapmirroring

PASCAL_78 — Fri, 07 Dec 2012 11:22:52 GMT

I disabled agregate snap sched on Nov 30, to see if agregate snapshots will be the same size in the future or not.

But i noticed that it was the same problem and agregate snapshot are using more and more space, so the agregate free space is goig down, whereas no agregate scheduling is active.

Re: Problem with agregate free space and snapmirroring

LTDCLSERGAO — Fri, 07 Dec 2012 14:13:03 GMT

OK.

Snapshots keep track of the blocks that have changed between snapshots and the current filesystem. The changes introduce to a filesystem can increases the snapshot size.

If you dont' need those snap, delete them.

Re: Problem with agregate free space and snapmirroring

PASCAL_78 — Mon, 10 Dec 2012 13:59:58 GMT

Thanks Said.

I deleted all existing agregate snapshots, I'll see tomorow if somme agregate snapshots will be generated or not.

I hope "no".

Re: Problem with agregate free space and snapmirroring

PASCAL_78 — Wed, 12 Dec 2012 09:12:33 GMT

All is ok now, no more agregate snapshots arre generated.

Thanks you Said.

Re: Problem with agregate free space and snapmirroring

uptimenow — Sun, 03 Mar 2013 10:36:21 GMT

Also note that when you delete aggregate snapshots, not all blocks are freed immediately. There's a WAFL scan running to reclaim the freed aggregate blocks ... This may distort any "df -A" or "aggr show_space" figures you look at.