Re: XFS for lots of small files

Martin Steigerwald
2008-05-25T11:38:05Z

Am Sonntag 25 Mai 2008 schrieb Eric Sandeen:
> Martin Steigerwald wrote:
> > And there is quite some fragmentation on it:
> >
> > xfs_db> frag
> > actual 653519, ideal 587066, fragmentation factor 10.17%
>
> No, there's not.

OK, so there is or better was (see below) *some* fragmentation.

> You have 653519 extents out of an "ideal" 587066.
>
> That is 653519/587066 = 1.113 extents per file.
>
> It is not "quite some" fragmentation, it is near perfect (although this
> is subjective, and also depends on the size of your files... if they
> are all 8k then 1.113 extents per file might be a bit high; if they
> average 1G then 1.113 extents on average is pretty darned good.)

They vary a lot. From KMail ~/Mail directory with hundred of thousands of
mails in maildir format to a picture and movie collection from various
digicams with 150KB over 2-4 MB to 50-200 MB in size and a music
collection and kernel sources and and and... would need to run a tool on
them to gather some statistic.

Anyway, nothing that can't be optimized:

shambala> xfs_db -r /dev/sda5
xfs_db> frag
actual 683648, ideal 617593, fragmentation factor 9.66%
xfs_db> quit

shambala> xfs_fsr /dev/sda5
/home start inode=0

shambala> xfs_db -r /dev/sda5
xfs_db> frag
actual 620316, ideal 617584, fragmentation factor 0.44%
xfs_db> quit

xfs_fsr copied over several gigabytes and the free space of the partition
temporarily more than once was 4 GB less than the 20 GB of free space it
had before and after invoking xfs_fsr ;)

Not that I noticed a difference up to now however.

Ciao,
--
Martin 'Helios' Steigerwald - http://www.Lichtvoll.de
GPG: 03B0 0D6C 0040 0710 4AFA B82F 991B EAAC A599 84C7