zfs status -d units not clear

[ioquatix]

The units are not clear

# zpool status -D
  pool: backup
 state: ONLINE
  scan: none requested
config:

        NAME                                        STATE     READ WRITE CKSUM
        backup                                      ONLINE       0     0     0
          ata-eSATA-2_ExternalRAID_WD-WCAZA6489285  ONLINE       0     0     0

errors: No known data errors

 dedup: DDT entries 3255693, size 311 on disk, 179 in core

311 whats? 179 whats?

[dasjoe]

It's bytes, your DDT has 3.2 M entries, each entry is using 311 bytes on disk and 179 in RAM.

So your DDT consumes 556 MB of RAM (3255693 * 179 bytes) and is 966 MB on disk, for a total size of 1.48 GB.

[ioquatix]

Thanks! Could be good if this was in the output of the command?

[behlendorf]

I wouldn't be opposed to adding a b suffix to those byte sizes.

[dogganos]

'In core' means RAM you say, but in many cases where RAM is not sufficient, DDT entries * size in core > system RAM, which cannot happen of course. So in practice, 'in core' means 'in RAM as much as it could, and the rest spilled on disk'. Is that correct? Is there a way to tell how much of the DDT is spilled on disk? This would be a nice thing, since the more of DDT is spilled on disk, the more write performance is severely impacted.