The copy problem is really the backup problem

Posted Jun 4, 2019 9:18 UTC (Tue) by jezuch (subscriber, #52988)
In reply to: The copy problem is really the backup problem by mcr
Parent article: The Linux "copy problem"

At least on btrfs that's:

btrfs subvolume snapshot -r
btrfs send
btrfs receive

But it does not work on per-file basis, unfortunately. And yes, btrfs defines its own serialization format.

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The copy problem is really the backup problem

Posted Jun 4, 2019 14:06 UTC (Tue) by mcr (subscriber, #99374) [Link] (1 responses)

What happens if a file is open (TXTBUSY)? or open O_DIRECT, or any of these other things that might be mutually exclusive with regular I/O?

The copy problem is really the backup problem

Posted Jun 19, 2019 21:32 UTC (Wed) by nix (subscriber, #2304) [Link]

btrfs send and receive are not regular I/O, so they work fine. (Though I'm not sure what happens in conjunction with O_DIRECT, which is a bit... hard to grasp the semantics of on a CoW filesystem in any case.)

(You don't get -ETXTBSY if you read a file in any case, only if you try to modify it.)