linux-ext4 - Re: File limit inside a single directory

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Message-Id: <B52A17D2-8AD8-4427-B1D3-2FE6DE21585B@dilger.ca>
Date:	Thu, 12 Feb 2015 17:55:14 -0700
From:	Andreas Dilger <adilger@...ger.ca>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	"suntrop@....de" <suntrop@....de>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: File limit inside a single directory

We started to have problems in our testing around 15M entries in one directory (depends on hashing, add/remove cycles), but 10-12M entries is probably safe unless the filenames are long (e.g. above 32 chars). 

Cheers, Andreas

> On Feb 12, 2015, at 12:35, Eric Sandeen <sandeen@...hat.com> wrote:
> 
>> On 2/12/15 1:16 PM, suntrop@....de wrote:
>> Hello, i’m using a CMS which puts many files inside a single
>> directory. I’m wondering what the maximum number of files is which
>> can reside inside said directory. Is there a number which should not
>> be exceeded on account of performance reasons e.g. Is there a
>> difference between ext3 and ext4?
>> 
>> Thanks!
> 
> for htree directories, you will be limited by the max size of the tree, which currently is of limited depth.  That limit then depends on block size and filename lengths.
> 
> for 4k blocks, and 40 char names, you max out at around 20 million directory entries, if my old spreadsheet is still correct.
> 
> That limit is the same for ext3 and ext4.
> 
> performance-wise, to be honest, I'm not sure.  how many inodes are you talking about?
> 
> -Eric
> 
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