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  • When you mentioned btrfs, you mean the designated backup server was using btrfs rather than zfs, right? You may still send the file system to a file on the destination server... Commented Aug 29, 2022 at 9:36
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    I'm consciously doing a bit of handwaving here because I don't feel I have the in-depth zfs experience needed to speak with any kind of authority, but I do know that you can send to a file, so you would not actually need to have a zfs filesystem waiting on the receiving end, just something big enough to store the filesystem as a file. Sending can, AFAIK, only be done on snapshots, but sending with -R (--replicate) will also send descendent filesystems. Commented Aug 29, 2022 at 9:48
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    When you say "and also no zpool can be created on the backup server", is that because there are no unused drives/partitions/block-devices on the backup server, or because the zfs module & zfs utils are not installed on it? A zpool can be created using one or more files instead of disks/partitions (just create the files first. see man zpool, search for Example 4). Alternatively, you can create a VM that has a zpool made from one or more virtual disks. Commented Aug 30, 2022 at 0:07
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    But if all you want is a temporary full backup while rebuilding the system, zfs send-ing to a file is good enough (it only becomes a pain if you also need to keep incremental backups and expire them as they get older...as in the Q you linked to). For just a one-off backup, you can save a full zfs send -R to a file on any kind of filesystem, and restore from it with zfs recv later. It's just a stream of data. Commented Aug 30, 2022 at 0:09
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    @cas pigz is much better in this case - parallelizing the compression will improve transfer speed considerably. As will avoiding an ssh connection - if it's safe to rsh, that'll be a lot faster, too. Also, use mbuffer in the pipeline as zfs send ... tends to send data in large bursts with relatively long idle periods between the bursts: zfs send ... | mbuffer ... | pigz ... | mbuffer ... | rsh someone@somehost split ... Commented Aug 31, 2022 at 17:24