linux-ext4 - Re: How many files to create in one directory?

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Message-ID: <20140127193950.GA20411@thunk.org>
Date:	Mon, 27 Jan 2014 14:39:50 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	Masato Minda <minmin@...s.co.jp>, linux-ext4@...r.kernel.org
Subject: Re: How many files to create in one directory?

> It will depend on the length of the filenames.  But by my calculations,
> for average 28-char filenames, it's closer to 30 million.

Note that there will be some very significant performance problems
well before a directory gets that big.  For example, just simply doing
a readdir + stat on all of the files in that directory (or a readdir +
unlink, etc.) will very likely result in extremely unacceptable
performance.

So if you can find some other way of avoiding allowing the file system
that big (i.e., using a real database instead of trying to use a file
system as a database, etc.), I'd strongly suggest that you consider
those alternatives.

Regards,

					- Ted
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