[SunHELP] UFS logging worth it?

[Bill Bradford]

On Tue, Nov 21, 2000 at 02:21:59PM +0100, Magnus Abrante wrote:
> Let me correct my previous message, if you dont have the logging
> turned on in the /etc/vfstab, the file system wont know that it is
> a logging filesystem upon reboot, thus it wont be using the logs
> for the fcsk. So if you just did a remount and turned on the logging
> feature without adding it to /etc/vfstab i dont think it will work.
> 	//Magnus

Yep, I've got all my ufs filesystems with "logging" under options in
/etc/vfstab.  

>From the mount_ufs manual page:

                logging | nologging
                      If  logging is specified, then  logging  is
                      enabled  for  the  duration  of the mounted
                      file system.  Logging  is  the  process  of
                      storing  transactions (changes that make up
                      a complete UFS operation) in a  log  before
                      the  transactions  are applied to the  file
                      system.  Once a transaction is stored,  the
                      transaction can be applied to the file sys-
                      tem later. This prevents file systems  from
                      becoming  inconsistent, therefore eliminat-
                      ing the need to run  fsck.   And,   because
                      fsck  can  be bypassed, logging reduces the
                      time required to  reboot  a  system  if  it
                      crashes,  or  after  an  unclean  halt. The
                      default behavior is  nologging.

                      The log is allocated from  free  blocks  on
                      the file system, and is sized approximately
                      1 Mbyte per 1 Gbyte of file system, up to a
                      maximum   of  64  Mbytes.  Logging  can  be
                      enabled on any  UFS, including  root   (/).
                      The  log created by UFS logging is continu-
                      ally flushed as it fills  up.  The  log  is
                      totally  flushed  when  the  file system is
                      unmounted or as a result of the  lockfs  -f
                      command.

so far, I see no evidence of the "This prevents file systems from 
becoming inconsistent, therefore eliminating the need to run fsck."

I see slight differences in some things, like "rm -rf" of a large
source tree returns a prompt instantly, but other than that, I see
no advantages to using UFS logging, as it appears to not function
as per the manual page says it should...

If only VxFS (Veritas Filesystem) was cheaper... 8-(

Bill

-- 
Bill Bradford
mrbill at mrbill.net
Austin, TX