UFS2 snapshots on large filesystems

[Eric Anderson]

Oliver Fromme wrote:
> Oliver Fromme <olli at lurza.secnetix.de> wrote:
>  > user <user at dhp.com> wrote:
>  > > On Sun, 6 Nov 2005, Eric Anderson wrote:
>  > > > [fsck on large file systems taking a long time]
>  > > 
>  > > Can you elaborate ?  Namely, how long on the 2GB filesystems ?
>  > 
>  > It depends very much on the file system parameters.  In
>  > particular, it's well worth to lower the inode density
>  > (i.e. increase the -i number argument to newfs) if you
>  > can afford it, i.e. if you expect to have fewer large
>  > files on the file system (such as multimedia files).
> 
> 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.  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.  I think your tests are interesting, 
however not very telling of many real-world scenarios.

Eric






-- 
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Eric Anderson        Sr. Systems Administrator        Centaur Technology
Anything that works is better than anything that doesn't.
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