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I know that, technically, an individual Windows XP directory can hold an immense number of files (over 4.29 billion, according to a quick Google search).

However, is there a practical ceiling where too many files in one directory starts having an impact on reads to those files?

If so, what factors would exacerbate or help the issue?

I ask because my employer has several hundred XP machines in the field at client sites, and the performance on some of the older ones is getting "sludgy."

The machines download and display client-defined images, and my supervisor and I suspect that our slacktastic approach to cache management could be to blame as some of the machines have tens of thousands of images on them. I'm trying to gather evidence to support or contest the theory before spending time on a coding fix.

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Note: Assuming NTFS, as no one in their right mind would use FAT for anything else than USB thumb drives or memory cards, let alone on a server (ok, that thought is scary).

Yes, there is a limit. Storing more files than particles in the universe may prove impractical. However, the actual limit is far lower.

NTFS has a maximum of 4,294,967,295 (232 − 1) files per volume. A few of those are already used by the file system itself and folder should count as files too.

Microsoft recommends that you turn off auto-generation of DOS-compatible short names if you move past 300,000 as finding a unique short name gets difficult then.

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fsutil behavior set disable8dot3 1 – grawity Mar 31 '10 at 18:32
Yeah, I know there's a limit. Thanks for confirming my brief research that it's just over 4.29 billion files. Do you know if the DOS-compatible short names thing is an issue down in the range of tens of thousands of files, rather than 300,000 files? – BlairHippo Mar 31 '10 at 19:12
I don't think there is any issue with tens thousands files in a folder. Nothing related to this has been found my friend ;) – r0ca Mar 31 '10 at 19:29
@Blair: Tens of thousands are not that many files. Also accessing them isn't a bottleneck in any case, if anything, then enumerating them would be. But not at those counts, usually. – Joey Apr 1 '10 at 8:00

Last time I checked I had 12000+ cookies in one folder. Removed approx. half of them and noticed no difference.

But that may be on the low end of your question. You should have given some real-world numbers in your question to get better answers.

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