Should I write compressed or uncompressed data to a ZFS dataset with compression on?

[ovizii]

I'm busy testing a new tool to backup a full HD and I can select for it to compress its output so I was wondering if there is a point in doing so as it writes to a share and the underlying ZFS dataset has compression enabled.

I'm thinking that if I disable compression in my backup tool, it will work faster and consume less CPU and the ZFS compression will do the job automatically?

Any thoughts on this?

 

[gpsguy]

My WAG is that the backup tool will do a much better job with compression, than FreeNAS will.

Why don't you try it, with and without compression and compare the results.

 

[ovizii]

I'm busy trying but it just one full backup will take quite long so I thought I'd ask, while waiting for the practical test to finish

 

[Robert Trevellyan]

I'd look at the storage consumed both ways, and whether having the backup tool not do compression saves any time (which is unlikely unless it's CPU-bound).

EDIT: either way, leave compression enabled on the dataset. There's unlikely to be any measurable cost, and there's a chance of a useful benefit.