Compaction and Data Protection Volumes

[TMADOCTHOMAS]

We just upgraded to OnTAP 9.1P8. Production system is AFF so compaction is working by default. DR system is FAS8060. I enabled compaction at the aggregate level, but when I tried to enable at the volume level, it was only enabled on the root volumes. Is that because the other volumes are data protection volumes? Is there any value in turning on compaction on this system under these circumstances?

[TMADOCTHOMAS]

I typed this post too soon. Looks like it did enable for every volume on one node, but not the other. Looks like I had a typo on one entry and it caused the others to not run.

I do have a related question. I don't want to run the scan-old-data command on every volume, but am wondering if MOVING the volumes between aggregates would cause compaction to take effect. Any ideas?

[Storagator_DB · Accepted solution]

If you have set on aggergates, volume move will do the job

[TMADOCTHOMAS]

Good to know, thank you!

[heightsnj]

I have two follow-ups:

1.  Is there any way can I check how much compaction saved on volumes? if so, what is the command?
      It seems to me I can only check on the aggregate.

2. while volume copy to a compaction enabled destiantion aggr,  the volume will be really compacted ?

[TMADOCTHOMAS]

@heightsnj, compaction is aggregate-level, that's why that's the only place you can check it. And yes, I did in fact move a bunch of volumes around and the compaction rate increased.

[heightsnj]

Thanks!

One more followup:

Let's say if I have a volume with no dedup and compression enabled on sas aggr. Then I do volume move to aff node, would this volume be deped and compressed while moved over to ssd? as by default, it will have dedup and compression enable, 

[TMADOCTHOMAS]

Not sure. You could enable it before moving and then move it to be sure. I would try one and see the results. 

[heightsnj]

I just did a test, the interesting is that if a volume without compression enabled on the source SAS aggr, then if I volume move to a SSD aggr which by default inline compression is enabled, when the move is completed, the compression is still not enabled. 

Why, should not it be enabled?

[TMADOCTHOMAS]

Is your SSD aggregate on an AFF system? If not, I'm not sure if turns on inline by default. Even if it's moved to AFF, I don't recall if it turns it on automatically with a vol move. The default definitely applies when creating new volumes on AFF.

[heightsnj]

Yes, SSD aggr I am referring to here is on AFF. Understood inline dedup/compression/compact will be turned on by default for new volumes.

But, I just don't understand why  volumes with no compresson on SAS from source node when moved to SSD@AFF, his compression would not be turned on as I already tried. I would like to know what the logic explanation is.