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

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Message-ID: <52E6B80D.7060807@redhat.com>
Date:	Mon, 27 Jan 2014 13:48:29 -0600
From:	Eric Sandeen <sandeen@...hat.com>
To:	"Theodore Ts'o" <tytso@....edu>
CC:	Masato Minda <minmin@...s.co.jp>, linux-ext4@...r.kernel.org
Subject: Re: How many files to create in one directory?

On 1/27/14, 1:39 PM, Theodore Ts'o wrote:
>> 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.

Yep, that's the max possible, not the max useable.  ;)

(Although, I'm not sure in practice what max useable looks like, TBH).

-Eric

> 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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