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I have a zpool with around 6TB of data on it (including snapshots for the child datasets). For the important data in it, I already have backups on filesystem level. As I need to perform some rather "dangerous" operations (i.e. this pool migration), I want to backup the whole pool to a different server.

In an ideal world, I would have used send and recv (like so). Unfortunately, this server is btrfs-based with no option to install zfs. When researching, people recommend just plain rsync (e.g. here) but as far as I can see, I would be back to filesystem level and more importantly, I'm not sure if the already existing dataset snapshots would still be intact. I basically just want to "freeze" the entire pool with a snapshot, send that off to the remote server and in case something goes wrong, restore the pool to the previous state (with ideally one command).

Therefore I'm looking for a solution to backup an entire zfs to a different server running a different filesystem, keeping all datasets and snapshots intact

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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

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You can check how to one-way mirror an entire zfs pool to another zfs pool

And you should not use -R, because it only working with snapshot. Basically, what I do is (local backup):

# zfs list NAME USED AVAIL REFER MOUNTPOINT zroot 530G 377G 96K none zroot/ROOT 78.2G 377G 96K none zroot/ROOT/gentoo 78.2G 377G 76.8G / zroot/data 405G 377G 96K none zroot/data/extra 202G 377G 202G /extra zroot/data/home 202G 377G 200G /home zroot/var 47.7G 377G 47.7G /var # zpool create zroot.backup /dev/sda # zfs send zroot | zfs recv -Fdu zroot.backup # zfs send zroot/ROOT | zfs recv -Fdu zroot.backup/ROOT # ...
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    Note that the target filesystem in the question is not ZFS. Commented Nov 30, 2024 at 15:53
  • Thanks for the reminder, since zfs send is just a byte stream, you can redirect it to any file and then recv. But I haven't actually tested how to split and transfer large files, so I only gave the backup and restore code. Commented Dec 2, 2024 at 6:42
  • What does your system do when you say zfs create zroot.backup ? Mine says cannot create 'zroot.backup': missing dataset name Commented Dec 2, 2024 at 7:13
  • @JimL. I think it's supposed to be root/backup. Commented Dec 2, 2024 at 8:16
  • @JimL. Sorry, my mistake, it should be zpool create zroot.backup /dev/sda in a new disk, or like @kusalananda say zroot/backup Commented Dec 3, 2024 at 7:04

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