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Joey Hess 2024-09-05 09:20:38 -04:00
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[[!comment format=mdwn
username="joey"
subject="""comment 1"""
date="2024-09-05T12:56:27Z"
content="""
The reason for reflink=always is that git-annex wants it to fail when
reflink is not supported and the copy is going to be slow.
Then it falls back to copying the file itself, which allows an interrupted
copy of a large file to be resumed, rather than restarted from the beginning
as cp would do when it's not making a reflink.
So, at first it seemed to me that the solution will need to involve
git-annex using `copy_file_range` itself.
But, git-annex would like to checksum the file as it's copying it (unless
annex.verify is not set), in order to avoid needing to re-read it to hash it
after the fact, which would double the disk IO in many cases.
Using `copy_file_range` by default would prevent git-annex from doing that.
So it needs to either be probed, or be a config setting. And whichever way
git-annex determines it, it may as well use `cp reflink=auto` then
rather than using `copy_file_range` itself.
I'd certainly rather avoid a config setting if I can. But if this is specific to
NFS on ZFS, I don't know what would be a good way to probe for that? Or is this
happening on NFS when not on ZFS as well?
"""]]