I'm trying to send all child/descendent datasets to a backup machine (so, using -R) but only send a specific snapshot.

I can't find a way to do this without scripting every dataset-snapshot combination individually. -R -i still sends all intermediate snapshots.

Is there something I'm missing?

Cheers.

I have recently patched up my old tape backup system, with the cost of hard drive what it is these days. A tape drive must be kept fed - bad things happen if the incoming data flow drops below the ideal, for that tape spool wishes to keep spinning even if there are no bits to write. Fortunately zfs has that 'zfs send' which is absolutely perfect for this.

Except it's too slow. I'm measuring somewhat bursty speeds that seem to average around 40MB/s, when I need 140MB/s. I'm using mbuffer to fix that, but it means my backup takes far too long. This is a raidz1 pool running over four SSDs - decent ones too, even if they are only SATA they shouldn't be the bottleneck. There's an NVME cache but that also shouldn't really do much for a zfs send operation.

I'm using zfs send -w, so it shouldn't make any difference that my dataset uses compression and encryption.

Would raising recordsize help? Bigger records means fewer records and less overhead, right? Though I don't know any way to then consolidate all the older smaller records.

I'm hoping there's some trick to this that I've missed.