linux-ext4 - Re: mkfs.ext4: high default -i value undocumented

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Message-ID: <49B53C20.1010206@redhat.com>
Date:	Mon, 09 Mar 2009 10:56:16 -0500
From:	Eric Sandeen <sandeen@...hat.com>
To:	Goswin von Brederlow <goswin-v-b@....de>
CC:	Jan Engelhardt <jengelh@...ozas.de>, linux-ext4@...r.kernel.org,
	kzak@...hat.com
Subject: Re: mkfs.ext4: high default -i value undocumented

Goswin von Brederlow wrote:
> Eric Sandeen <sandeen@...hat.com> writes:
> 
>> Jan Engelhardt wrote:
>>> Hi,
>>>
>>>
>>> Creating an ext4 filesystem on a 4 GB image file (to be loop-mounted 
>>> later) gives me 256K inodes. Choosing -i 4096 instead gives 1M, which 
>>> would mean the default for -i is 16384. 
>> That's right, look in /etc/mke2fs.conf:
>>
>> [defaults]
>>         base_features =
>> sparse_super,filetype,resize_inode,dir_index,ext_attr
>>         blocksize = 4096
>>         inode_size = 256
>>         inode_ratio = 16384
>>
>>> Besides me finding 16384 a 
>>> little unreasonable (XFS offers 2M inodes by default), 
>> XFS is a totally different beast, because it dynamically allocates
>> inodes.  It doesn't really offer *anything* by default.
>>
>> Which part of a 16384-data-bytes-to-inode-count ratio do you find
>> unreasonable?  Do you find it unreasonably high, or unreasonably low?
> 
> Too high for 4G, to low for 6 TiB.

I think it's hard to make a blanket statement like that; it depends very
much on the average size of the files on the fs.

The only thing that makes it too high or too low is whether the average
file size is significantly different than 16k, really (with the caveat
that we should bias towards overprovisioning vs. underprovisioning, by
default)

-Eric

> MfG
>         Goswin

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