ZFS replication with zfs send is the fastest option to copy or sync two filesystems on the same or different servers. As it is based on snaps it includes open files. Replication starts with a complete transfer of the whole filesystem based on a snapshot. After then only modified datablocks based on following delta-snaps need to be transferred as a datastream without a filecompare like rsync is needing and what makes it slow with a high storage load. ZFS works more like a radio transmission that you can record. This allows to keep two filesystems in sync down to a minute delay even on high load servers in the Petabyte range.
As on every incremental replication run, a target filesystem starts a rollback to a common base snap, all snaps that you create manually or via autosnap jobs after the last replication run are deleted then.
If you want to keep snaps on a backup machine with active replications, this can be very complicated as you must either manually care about or you need a replication script where you can setup a snap history/ retention policy.
For napp-it I included such a retention policy in current version 17.03dev where you can set for example
keep = hours:24,days:32,months:12,years:3
This means keep one replication snap per hour for current day, one snap per day for last 32 days, one snap per month for last 12 months and one snap per year for last 3 years
Additionally you can set hold=10 (hold all snaps for 3 days) or hold=10s (hold last 10 snaps)
see https://www.napp-it.org/doc/downloads/napp-it.pdf page 55
As on every incremental replication run, a target filesystem starts a rollback to a common base snap, all snaps that you create manually or via autosnap jobs after the last replication run are deleted then.
If you want to keep snaps on a backup machine with active replications, this can be very complicated as you must either manually care about or you need a replication script where you can setup a snap history/ retention policy.
For napp-it I included such a retention policy in current version 17.03dev where you can set for example
keep = hours:24,days:32,months:12,years:3
This means keep one replication snap per hour for current day, one snap per day for last 32 days, one snap per month for last 12 months and one snap per year for last 3 years
Additionally you can set hold=10 (hold all snaps for 3 days) or hold=10s (hold last 10 snaps)
see https://www.napp-it.org/doc/downloads/napp-it.pdf page 55
