Help - Previous snapshots appear to have doubled in size?

[markey164]

Hi all,

I have a 7TB vol (98% full) with 10% snapshot reserve. Its close to the limit so we are monitoring closely whilst planning a move to another Netapp.

At 10am morning I noted ~50GB free in the snapshot reserve. I then deleted 4 of the oldest snapshots (~100GB) which *should* have given me ~150GB free in the snapshot reserve.

However on checking the vol later at 3pm, I found that snapshot usage had gone 420GB OVER instead of the expected 150GB under! but why?

Looking at the only 2 snapshots that have run today (7am and 1pm), they are 22Gb and 10GB in size, so don't not reflect this sudden increase in snapshot usage today. Its as if something else has consumed the snapshot reserve space.

I then noticed that the snapshots for this volume (we keep 2 a day for 14 days),  all now appear to have doubled in size from what they were previously!!, but I can't see how that is possible or what could have caused this.

Anyone any ideas?

Cheers

Mark

[JGPSHNTAP]

Please provide df -Vg and snap list of the volume.   (please sanitize the data before posting)

[markey164]

Here's the df and snap list output (sanitised)

df -Vg

/vol/VolX/            6497GB     6393GB      104GB      98%  /vol/VolX/

/vol/VolX/.snapshot      721GB      424GB      297GB      59%  /vol/VolX/.snapshot

filer> snap list VolX
Volume VolX
working...

%/used %/total date name
---------- ---------- ------------ --------
0% ( 0%) 0% ( 0%) Oct 30 13:00 hourly.0
1% ( 0%) 1% ( 0%) Oct 30 07:00 hourly.1
1% ( 0%) 1% ( 0%) Oct 30 00:30 DRFiler(0118052894)_dfpm_VolX_SM_1218465977_2604.1889 (snapmirror)
1% ( 1%) 1% ( 1%) Oct 29 13:00 hourly.2
2% ( 1%) 2% ( 0%) Oct 29 07:00 hourly.3
3% ( 1%) 2% ( 1%) Oct 28 13:00 hourly.4
3% ( 1%) 3% ( 1%) Oct 28 07:00 hourly.5
4% ( 1%) 4% ( 1%) Oct 27 13:00 hourly.6
5% ( 1%) 4% ( 1%) Oct 27 07:00 hourly.7
5% ( 0%) 4% ( 0%) Oct 26 13:00 hourly.8
5% ( 0%) 4% ( 0%) Oct 26 07:00 hourly.9
5% ( 0%) 4% ( 0%) Oct 25 13:00 hourly.10
5% ( 0%) 4% ( 0%) Oct 25 07:00 hourly.11
5% ( 1%) 5% ( 0%) Oct 24 13:00 hourly.12
7% ( 2%) 7% ( 2%) Oct 24 07:00 hourly.13
8% ( 1%) 8% ( 1%) Oct 23 13:00 hourly.14
8% ( 1%) 8% ( 0%) Oct 23 07:00 hourly.15
9% ( 1%) 9% ( 1%) Oct 22 13:00 hourly.16
10% ( 1%) 9% ( 1%) Oct 22 07:00 hourly.17
10% ( 1%) 10% ( 1%) Oct 21 13:00 hourly.18
11% ( 1%) 10% ( 0%) Oct 21 07:00 hourly.19
11% ( 1%) 11% ( 1%) Oct 20 13:00 hourly.20
13% ( 3%) 13% ( 2%) Oct 20 07:00 hourly.21
13% ( 0%) 14% ( 0%) Oct 19 13:00 hourly.22
14% ( 0%) 14% ( 0%) Oct 19 07:00 hourly.23
14% ( 0%) 14% ( 0%) Oct 18 13:00 hourly.24
14% ( 0%) 14% ( 0%) Oct 18 07:00 hourly.25
14% ( 1%) 14% ( 1%) Oct 17 13:00 hourly.26

Ok so that was VERY interesting. df -Vg says I have 297GB free in my snapshot reserve (which is what i would expect), whilst running the normal tools, ie snap list volname, or looking in the OnCommand System manager GUI, both show the snapshots as being 250GB *over* capacity.

Anyone know why the discrepancy here?