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Ufs_logging.txt Guest on 23rd September 2020 05:44:55 PM
  1. Reduce FSCK times for UFS based file systems on Solaris 7 and later...
  2.  
  3. On Solaris 7 and later, the UFS file system code was extended to provide file system logging.
  4. When enabled, all changes to file system meta-data are written to an intent log prior to being
  5. written out to the file system itself. If the machine then crashes, the log is used to roll back
  6. any unfinished changes to the meta-data, negating the need to analyse the file system structures.
  7. This reduces fsck times to a matter of seconds.
  8.  
  9. To enable this facility simply specify the logging mount option in /etc/vfstab.
  10.  
  11.  
  12. From the mount_ufs man page...
  13. ------------------------------
  14. logging | nologging
  15.       If  logging is specified, then  logging  is
  16.       enabled  for  the  duration  of the mounted
  17.       file system.  Logging  is  the  process  of
  18.       storing  transactions (changes that make up
  19.       a complete UFS operation) in a  log  before
  20.       the  transactions are  applied to the  file
  21.       system.  Once a transaction is stored,  the
  22.       transaction can be applied to the file sys-
  23.       tem later. This prevents file systems  from
  24.       becoming  inconsistent, therefore eliminat-
  25.       ing the need to run  fsck.   And,   because
  26.       fsck  can  be bypassed, logging reduces the
  27.       time required to  reboot  a  system  if  it
  28.       crashes,  or  after  an  unclean  halt. The
  29.       default behavior is  nologging.
  30.  
  31.       The log is allocated from  free  blocks  on
  32.       the file system, and is sized approximately
  33.       1 Mbyte per 1 Gbyte of file system, up to a
  34.       maximum   of  64  Mbytes.  Logging  can  be
  35.       enabled on any  UFS, including  root   (/).
  36.       The  log created by UFS logging is continu-
  37.       ally flushed as it fills  up.  The  log  is
  38.       totally  flushed  when  the  file system is
  39.       unmounted or as a result of the  lockfs  -f
  40.       command.
  41.  
  42.  
  43. -Ken Robson

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