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old version?

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Joey Hess 2012-01-27 16:50:27 -04:00
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doc/bugs/copy_doesn__39__t_scale.mdwn
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It seems that git-annex copies every individual file in a separate transaction. This is quite costly for mass transfers: each file involves a separate rsync invocation and the creation of a new commit. Even with a meager thousand files or so in the annex, I have to wait for fifteen minutes to copy the contents to another disk, simply because every individual file involves some disk thrashing. Also, it seems suspicious that the git-annex branch would get a thousands commits of history from the simple procedure of copying everything to a new repository. Surely it would be better to first copy everything and then create only a single commit that registers the changes to the files' availability? It seems that git-annex copies every individual file in a separate
transaction. This is quite costly for mass transfers: each file involves a
separate rsync invocation and the creation of a new commit. Even with a
meager thousand files or so in the annex, I have to wait for fifteen
minutes to copy the contents to another disk, simply because every
individual file involves some disk thrashing. Also, it seems suspicious
that the git-annex branch would get a thousands commits of history from the
simple procedure of copying everything to a new repository. Surely it would
be better to first copy everything and then create only a single commit
that registers the changes to the files' availability?
(I'm also not quite clear on why rsync is being used when both repositories are local. It seems to be just overhead.) > git-annex is very careful to commit as infrequently as possible,
> and the current version makes *1* commit after all the copies are
> complete, even if it transferred a billion files. The only overhead
> incurred for each file is writing a journal file.
> You must have an old version.
> --[[Joey]]
(I'm also not quite clear on why rsync is being used when both repositories
are local. It seems to be just overhead.)
> Even when copying to another disk it's often on
> some slow bus, and the file is by definition large. So it's
> nice to support resumes of interrupted transfers of files.
> Also because rsync has a handy progress display that is hard to get with cp.
>
> (However, if the copy is to another directory in the same disk, it does
> use cp, and even supports really fast copies on COW filesystems.)
> --[[Joey]]