btrfs equivalent for zfs send -R
Hi all.
If I have a btrfs subvolume 'subv' and then subvolumes subv/sub1, subv/sub2, subv/sub3, is there a way to snapshot all the subv tree and then recursively send it remotely?
I think this would be the analogous of zfs snapshot -r, and then zfs send -R.
thanks!
Giorgos
Γιώργος Πάλλας posted on Sat, 27 Feb 2016 13:45:03 +0200 as excerpted:
Quoted 8 lines
Hi all.
If I have a btrfs subvolume 'subv' and then subvolumes subv/sub1, subv/sub2, subv/sub3, is there a way to snapshot all the subv tree and then recursively send it remotely?
I think this would be the analogous of zfs snapshot -r, and then zfs send -R.
As a list regular and btrfs user myself, but not a dev...
No idea about zfs and my own btrfs use-case doesn't use btrfs send/ receive either, so this is primarily from previous list posts, with a quick look at the (v4.4.1) btrfs-send manpage as well...
Recursive send isn't yet supported, only one at a time.
Based on a previous comment from someone who apparently looked at the code (but isn't a btrfs dev either), there's possibly some code for -r (recursive) already in the repo (or maybe it's simply a comment reserving the -r option?), but it doesn't work yet.
However, it shouldn't be horribly difficult to hack up scripts that automate the otherwise manual recursive-send/receive for you, as I'd very likely do myself if I needed that functionality. =:^)
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Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
Quoted 19 lines · Duncan
Γιώργος Πάλλας posted on Sat, 27 Feb 2016 13:45:03 +0200 as excerpted:
Quoted 8 lines
Hi all.
If I have a btrfs subvolume 'subv' and then subvolumes subv/sub1, subv/sub2, subv/sub3, is there a way to snapshot all the subv tree and then recursively send it remotely?
I think this would be the analogous of zfs snapshot -r, and then zfs send -R.
As a list regular and btrfs user myself, but not a dev...
No idea about zfs and my own btrfs use-case doesn't use btrfs send/ receive either, so this is primarily from previous list posts, with a quick look at the (v4.4.1) btrfs-send manpage as well...
Recursive send isn't yet supported, only one at a time.
Quoted 9 lines
Based on a previous comment from someone who apparently looked at the code (but isn't a btrfs dev either), there's possibly some code for -r (recursive) already in the repo (or maybe it's simply a comment reserving the -r option?), but it doesn't work yet.
However, it shouldn't be horribly difficult to hack up scripts that automate the otherwise manual recursive-send/receive for you, as I'd very likely do myself if I needed that functionality. =:^)
Thanks for the reply Duncan.
The problem with scripting the recursive process, as I understand it, is that in the case of e.g. adding an identical file inside each one sub subvolume, this file would have to be transmitted during send, so many times as the number of the sub subvolumes, which of course is not viable. Am I right?
Giorgos
Γιώργος Πάλλας posted on Sun, 28 Feb 2016 10:17:38 +0200 as excerpted:
Quoted 18 lines · Duncan
Quoted 17 lines
Γιώργος Πάλλας posted on Sat, 27 Feb 2016 13:45:03 +0200 as excerpted:
Quoted 8 lines
Hi all.
If I have a btrfs subvolume 'subv' and then subvolumes subv/sub1, subv/sub2, subv/sub3, is there a way to snapshot all the subv tree and then recursively send it remotely?
I think this would be the analogous of zfs snapshot -r, and then zfs send -R.
As a list regular and btrfs user myself, but not a dev...
No idea about zfs and my own btrfs use-case doesn't use btrfs send/ receive either, so this is primarily from previous list posts, with a quick look at the (v4.4.1) btrfs-send manpage as well...
Quoted 5 lines
Quoted 5 lines
Recursive send isn't yet supported, only one at a time.
Based on a previous comment from someone who apparently looked at the code (but isn't a btrfs dev either), there's possibly some code for -r (recursive) already in the repo (or maybe it's simply a comment
reserving
Quoted 4 lines
Quoted 4 lines
the -r option?), but it doesn't work yet.
However, it shouldn't be horribly difficult to hack up scripts that automate the otherwise manual recursive-send/receive for you, as I'd
very
Quoted 10 lines
Quoted 2 lines
likely do myself if I needed that functionality. =:^)
Thanks for the reply Duncan.
The problem with scripting the recursive process, as I understand it, is that in the case of e.g. adding an identical file inside each one sub subvolume, this file would have to be transmitted during send, so many times as the number of the sub subvolumes, which of course is not viable. Am I right?
As I understand it, no. What you're looking for is the -c <clone-src> option. While there can be only one parent, many clone-sources are allowed. Send does transfer a bit more metadata for clone-sources than it does for parents, but where it finds a clone, it's just that metadata, not the whole file.
I /suspect/, however, that running dedup on the clone-sources first, such that the sources do share reflinks with the sent subvolume, will increase the hit-rate on the clones. I suspect that if the same file is separately added, without dedup, so the sources have multiple copies, not a shared copy, btrfs send won't detect the dups at send-time because they're not reflinking the same extents and thus aren't, to btrfs, duplicates.
The inline dedup patches now being processed should help in that regard, however, avoiding having to run a separate dedup later, as has been the case with dedup so far.
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Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman
Quoted 8 lines · Γιώργος Πάλλας
Hi all.
If I have a btrfs subvolume 'subv' and then subvolumes subv/sub1, subv/sub2, subv/sub3, is there a way to snapshot all the subv tree and then recursively send it remotely?
I think this would be the analogous of zfs snapshot -r, and then zfs send -R.
There's no recursive snapshotting in Btrfs. There is btrfs send -e which I think is close to zfs send -I but at the moment it's broken.
https://bugzilla.kernel.org/show_bug.cgi?id=111221
The man page for send suggests -e is using a different format, so I'm gonna guess the send format isn't stable yet.
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Chris Murphy