* Re: dedup and receive -p
2016-03-14 12:39 dedup and receive -p Sylvain Joyeux
@ 2016-03-15 0:49 ` Duncan
0 siblings, 0 replies; 2+ messages in thread
From: Duncan @ 2016-03-15 0:49 UTC (permalink / raw)
To: linux-btrfs
Sylvain Joyeux posted on Mon, 14 Mar 2016 09:39:51 -0300 as excerpted:
> I was trying to find a definitive information about this, but could not
> ...
>
> AFAIK, defrag breaks CoW and send/receive -p. I was wondering whether
> deduplication would break it too, i.e. if doing a send/receive to
> transfer a subvolume, running dedup, and then using said subvolum as a
> parent with send -p would work or not.
I believe it would... if done as you posted. But this seems blindingly
obvious to me so I think either the scenario you posted didn't actually
match what you intended in your head, or there's a misunderstanding on
either your part or mine.
The better method would be to do the dedup, take a read-only snapshot of
the subvolume, send/receive it (of course send/receive already works with
snapshots, but this is making it explicit), and keep that snapshot around
to do the later send -p from.
You could then continue using the subvolume itself without worrying about
changing it in ways incompatible with send -p, because you'd be changing
the subvolume, not the read-only snapshot you took of it for the send,
which would remain unchanged and thus could be used as the basis of a
later send -p without a problem.
But like I said using the read-only snapshot for both the original send
and as the parent in the later send -p seems blindingly obvious to me, so
I think somewhere along the line some signals got crossed and I'm not
sure if you didn't write what you actually intended, or if either you or
I misunderstood something somewhere along the line.
--
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
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