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Date:      Mon, 14 Nov 2005 11:44:08 +0100 (CET)
From:      Oliver Fromme <olli@lurza.secnetix.de>
To:        freebsd-fs@FreeBSD.ORG
Subject:   Re: UFS2 snapshots on large filesystems
Message-ID:  <200511141044.jAEAi8bg020303@lurza.secnetix.de>
In-Reply-To: <43779EB1.5070302@centtech.com>

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Eric Anderson <anderson@centtech.com> wrote:
 > Oliver Fromme wrote:
 > > I just accidentally pulled the wrong power cord ...
 > > So now I can give you first-hand numbers.  :-}
 > > 
 > > This is a 250 Gbyte data disk that has been newfs'ed
 > > with -i 65536, so I get about 4 million inodes:
 > > 
 > >       Filesystem     iused      ifree  %iused
 > >       /dev/ad0s1f  179,049  3,576,789     5%
 > > 
 > > So I still have 95% of free inodes, even though the
 > > filesystem is fairly good filled:
 > > 
 > >       Filesystem     1K-blocks         Used       Avail  Capacity
 > >       /dev/ad0s1f  237,652,238  188,173,074  30,466,986     86%
 > > 
 > > fsck(8) took about 2 minutes, which is acceptable, I
 > > think.  Note that I always disable background fsck
 > > (for me personally, it has more disadvantages than
 > > advantages).
 > > 
 > > This is what fsck(8) reported when the machin came
 > > back up:
 > > 
 > >       /dev/ad0s1f: 179049 files, 94086537 used, 24739582 free
 > >       (26782 frags, 3089100 blocks, 0.0% fragmentation)
 > 
 > 180k inodes seems like a pretty small amount to me.

It's my multimedia disk.  It contains mainly multimedia
files, such as images, audio and video files.

 > Here's some info from some of my filesystems:
 > 
 > # df -i
 > Filesystem      1K-blocks        Used      Avail Capacity  iused     ifree %iused  Mounted on
 > /dev/amrd0s1d     13065232    1109204   10910810     9%      663   1695079    0%   /var
 > /dev/label/vol1 1891668564 1494254268  246080812    86% 68883207 175586551   28%   /vol1
 > /dev/label/vol2 1891959846  924337788  816265272    53% 59129223 185364087   24%   /vol2
 > /dev/label/vol3 1892634994 1275336668  465887528    73% 31080812 213506706   13%   /vol3
 > 
 > Even /var has over 1million.

No.  Your /var has just 663 inodes in use, and it has about
1.7 million unused inodes which is just a waste.

Your other file systems use much more inodes, but they're
also much bigger (2 Tbyte) than mine, and they seem to
contain different kind of data.

 > I think your tests are interesting, 
 > however not very telling of many real-world scenarios.

As mentioned above, my "test" was done on my multimedia
file system with an average file size of roughly 1 Mbyte.
Such file systems are quite real-world.  :-)

On a file system containing exclusively video files, innd
cycle buffers or similarly large files, the inode density
can be reduced even further.  If you have a 2 Tbyte file
system that contains only a few thousand files, then you're
wasting 60 Gbytes for unused inode data.

Of course, if you design a file system for different
purposes, your requirements might be completely different.
A maildir server or squid proxy server definitely requires
a much higher inode density, for example.

Best regards
   Oliver

-- 
Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
Any opinions expressed in this message may be personal to the author
and may not necessarily reflect the opinions of secnetix in any way.

Perl is worse than Python because people wanted it worse.
        -- Larry Wall



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