File system performance

[Bill Vermillion]

In article <1990Nov3.124110.2155 at metro.ucc.su.OZ.AU> dawes at suphys.physics.su.OZ.AU (David Dawes) writes:
>From article <294 at audfax.audiofax.com>, by arnold at audiofax.com (Arnold Robbins):
>> rcd at ico.isc.com (Dick Dunn) writes:
>>>  The BSD-style file system is a far better performer.
>> 
>> In article <1990Nov01.114726.14348 at nstar.uucp> larry at nstar.uucp (Larry Snyder) writes:
>>>Yes - but 8K blocks - just think what that would do to your partition
>>>with all the news articles --
   
>> I have to testify as to the speed of the BSD filesystem.  When we switched
>> to it with ESIX rev D our systems sped up very noticeably!
 

>I too am using ESIX rev D with ffs.  One of my file systems became heavily
>fragmented, and got to the point where there were 0 free blocks, and
>5000 free frags.  df reported 10000 blocks free, but attempting to write
>to the file system resulted in "Disk full" errors.  This meant that I
>had an unusable 5MB on a 65MB file system. (BTW, there were plenty of free
>inodes.)
 
>Is this how FFS is supposed to work, or is there a problem with the ESIX
>implementation?

That's about the right amount.  Check your manual in the newfs entry or the
ffsmkfs entry, and you will see that 10% of the disk is reserved and can
NOT be used by anyone except the super user.  That disk is full 0%, as far
as a regular user is concerned.

I just remade a fs last night, and found one other interesting thing.
You can set how many inodes there are in the system, but the -i flag
doesn't work, but changing the number of cylinder groups does.

I made a fs with 95000+ inodes, and got a warning installing it saying it
may (it did not say would, just may) cause a system PANIC.

So I decided to take a look.  I had cpio'ed the entire news hierarchy onto
another partition to be able to add more inodes (I took default the first
time and didn't have enough).

When I cpio'ed them back, many attempts to put files in their proper place
came back with "not a directory" type error messages.  Sometimes
directories would be created, other times files with directory names would
be created and then subsequent writes went awry.

I remade the fs with just about 65000 inodes using a smaller numbers of
cylinders per cylinder group, and it came out to about 6.5 megs per c/g,
and appears to be working just fine.

There is a description of the file system in the manual.  Talking with a
friend of mine about this problem last night, it appears the Esix ffs is
only partially BSD, because he said I should have no inode limits on a pure
BSD file system.   Other than that the ffs system seems to be a good
performer.


-- 
Bill Vermillion - UUCP: uunet!tarpit!bilver!bill
                      : bill at bilver.UUCP