aggr show_space interpretation

Hi all,

Currently I'm looking into a NetApp filer for which snapvault replication has issues because there is not enough space on the primary side to keep all changes in a snapshot.

I started looking at the output of aggr show_space -h and I wonder where some of the space goes.

I assume Usable space = total space(18TB) - WAFL Reserve (1913GB) - Snap Reserve (344GB).

Is A-SIS space that is taken out of the aggregate usable space?

Space allocated to volumes in the aggregate are Total Space allocated at the bottom of the output.

Used is the sum of the usage of all volumes. Usage of volumes is the sum of data and snapshots in that volume.

Please correct me if I got anything of this wrong.

This is what I can't decipher where space is going:

Aggregate                       Allocated            Used           Avail

Total space                          15TB            10TB           560GB

4,5TB is gone for some reason: 15TB- 10TB = 560GB?

What am I missing here? Are there any other things that should be kept in account? Can someone give a drill down of all elements that are used to get to this number?

Are LUNs counted fully even half of the amount is used?

Is the target free space of a volume also taken into account?

As the volume usage seems correct, then we loose +4TB on the aggregate level? On what?

This is an example:

Aggregate 'aggr0_xxx_fc'

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

           18TB          1913GB           344GB            16TB             0KB           919GB             0KB

Space allocated to volumes in the aggregate

Volume                          Allocated            Used       Guarantee

root_vol_delng153                   162GB          8172MB          volume

vol0              1350GB          1201GB          volume

vol1              1348GB           940GB          volume

vol2              1348GB          1012GB          volume

vol3              1348GB           792GB          volume

vol16             1348GB          1097GB          volume

vol17             1347GB           864GB          volume

vol18             1348GB           856GB          volume

vol32             1372GB           802GB          volume

vol45             2212GB          1663GB          volume

vol46             2213GB          2002GB          volume

Aggregate                       Allocated            Used           Avail

Total space                          15TB            10TB           560GB

Snap reserve                        344GB           217GB           127GB

WAFL reserve                       1913GB           205GB          1708GB

Thanks in advance!

Re: aggr show_space interpretation

For thick volumes (with reservation “volume”) full size is reserved in aggregate when volume is created and not available for anything else. “Used” shows actually used space and the rest is space reserved for volumes. If you sum all space allocated for volumes, you get ~ 15TB.

Re: aggr show_space interpretation

Thanks for that Aborzenkov!

Just one more thing that I wonder. IIRC you need to keep some space free for the SIS db on both the volume and the aggregate.

Is this space allocated in the WAFL reserve? I would think not.