ZFS Setting up incremental zfs backups to external hard drive

Hi,

I have an external hard drive connected to my NAS, and I am getting nightly backups of some datasets into this drive. There are daily snapshots taken from these datasets, which revolve on a weekly fashion; when taking a snapshot today, the snapshot from 7-days-ago gets destroyed. Therefore, each dataset has a 7-day-long snapshot history at any given time. This is the command I use for backing up:
zfs send -RI pool0/media@yesterday pool0/media@today | zfs receive -Fu external/backup/pool0_media
My problem is that zpool list shows about 81% of the external drive allocated, whereas I feel like it should be less than that based on the backed up actual dataset sizes. I guess one reason for that discrepancy may be the child snapshots under each dataset. Is there a more space-saving strategy that can be used for this purpose? I don't want to run out of external drive space? Am I supposed to use -Ri instead of -RI?

My confusion is partly because of the discrepancy between zpool list and df -h outputs. The former shows the external drive pool at 81% capacity with 5.92 TB allocated, whereas the latter shows less than 2.5 TB allocated in that drive.
 
You could increase compression level and enable dedup on your external drive. That'll only work on all new writes, so you'd have to copy it to a separate dataset to see how it'd change space usage.
 
Back
Top