44 lines
2 KiB
Markdown
44 lines
2 KiB
Markdown
git-annex is designed for scalability. The key points are:
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* Arbitrarily large files can be managed. The only constraint
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on file size are how large a file your filesystem can hold.
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While git-annex does checksum files by default, there
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is a [[WORM_backend|backends]] available that avoids the checksumming
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overhead, so you can add new, enormous files, very fast. This also
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allows it to be used on systems with very slow disk IO.
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* Memory usage should be constant. This is a "should", because there
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can sometimes be leaks (and this is one of haskell's weak spots),
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but git-annex is designed so that it does not need to hold all
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the details about your repository in memory.
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The one exception is that [[todo/git-annex_unused_eats_memory]],
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because it *does* need to hold the whole repo state in memory. But
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that is still considered a bug, and hoped to be solved one day.
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Luckily, that command is not often used.
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* Many files can be managed. The limiting factor is git's own
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limitations in scaling to repositories with a lot of files, and as git
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improves this will improve. Scaling to hundreds of thousands of files
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is not a problem, scaling beyond that and git will start to get slow.
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To some degree, git-annex works around innefficiencies in git; for
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example it batches input sent to certian git commands that are slow
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when run in an emormous repository.
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* It can use as much, or as little bandwidth as is available. In
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particular, any interrupted file transfer can be resumed by git-annex.
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## scalability tips
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* If the files are so big that checksumming becomes a bottleneck, consider
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using the [[WORM_backend|backends]]. You can always `git annex migrate`
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files to a checksumming backend later on.
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* If you're adding a huge number of files at once (hundreds of thousands),
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you'll soon notice that git-annex periodically stops and say
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"Recording state in git" while it runs a `git add` command that
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becomes increasingly expensive. Consider adjusting the `annex.queuesize`
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to a higher value, at the expense of it using more memory.
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