Arch Linux

Resistance

Member

Registered: 2012-09-04

Posts: 26

[SOLVED][ext4]Tuning "bytes-per-inode ratio" ?

Hi,

I'd like to format two partitions (under LVM) with ext4, a / (20GB) and a /home (890GB). The usage pattern for the /home partition will be fairly standard (smalls documents, configuration files, a lot of media).

The wiki mentions something about tuning the "bytes-per-inode ratio" for partition of more than 750GB (https://wiki.archlinux.org/index.php/Ex … filesystem).

It does however not reference any links / documentation for it.
The mke2fs man page isn't any more helful toward offering pragmatic advice.

My question is the following : Should I bother tuning this option for /home (I'm assuming that the default is good enough for /, correct?) and if so, how (range of ratios from "conservative" to "probably too much") ?

Thank you for reading.

Last edited by Resistance (2015-05-10 14:48:19)

Soukyuu

Member

Registered: 2014-04-08

Posts: 854

Re: [SOLVED][ext4]Tuning "bytes-per-inode ratio" ?

You probably should. The difference with a 1TB drive is about 22GB, apparently.
I remember having only 910GB after formatting my drive as well. I then reformatted the drive with different bytes-per-inode ratio and removed reserved blocks. Now I have a 930GB partition.

I can't seem to find the link where I found how to change the inode ratio, though, try google.
edit: actually, it seems it's the last post of that thread I linked.

Last edited by Soukyuu (2015-05-10 10:48:50)

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Resistance

Member

Registered: 2012-09-04

Posts: 26

Re: [SOLVED][ext4]Tuning "bytes-per-inode ratio" ?

Thank you for your reply.

After reading some stuff I'll simply go with "mkfs.ext4 -T largefile -m 1" for /home and the defaults for /.

http://arstechnica.com/civis/viewtopic.php?t=1125027
https://www.eskimo.com/linux/filesys.html
https://wiki.archlinux.org/index.php/Ex … ved_blocks

mwillems

Member

Registered: 2014-08-09

Posts: 89

Re: [SOLVED][ext4]Tuning "bytes-per-inode ratio" ?

1) Removing reserved blocks can result in an immediate gain of up to 5% space (although reducing it to 0 is kind of risky if you plan on actually filling the drive).
2) The defaults for inode creation is 1 inode for every 16MB of data.  inodes occupy 256 bytes.  That means for every 16M of data you lose 256 bytes, or about 1.5%.  I've confirmed that to be the case using df and df -i  on drives of various sizes and doing the math. 

The thread linked above showed 22GB for a 1.5T drive which is roughly 1.5%. So you can reduce your inodes and maybe squeeze out another percent or so, but TMK you can't undo it without reformatting.  If you haven't removed reserved blocks yet, that's a more fruitful source of disk space.

EDIT: Sorry, didn't see your [SOLVED] post until after I posted.  Sounds like you made the right call.

Last edited by mwillems (2015-05-10 15:06:25)