ru.unix.bsd

 
 - RU.UNIX.BSD ------------------------------------------------------------------
 From : Slawa Olhovchenkov                   2:5030/500     13 Sep 2007  14:37:30
 To : Victor Sudakov
 Subject : newfs -i
 -------------------------------------------------------------------------------- 
 

 
 13 Sep 07, Victor Sudakov writes to Slawa Olhovchenkov:
 
  >>  VS> Остались ли применительно к современной FreeBSD и современным
  >>  VS> объёмам дисков какие-то соображения, по которым следовало бы менять
  >>  VS> параметр -i при создании файловой системы?
 
  >>  VS> Hапример, пытаться выгадать место, поставив -i побольше.
 
  >> при -i побольше скорость записи крупных файлов будет тоже побольше. не на
  >> много, но измерению поддаются.
 
  VS> Интересно.
 
 bde         2007-07-10 13:20:24 UTC
 
   FreeBSD src repository
 
   Modified files:
     sys/fs/msdosfs       msdosfs_fat.c msdosfsmount.h
   Log:
   Don't use almost perfectly pessimal cluster allocation.  Allocation
   of the the first cluster in a file (and, if the allocation cannot be
   continued contiguously, for subsequent clusters in a file) was randomized
   in an attempt to leave space for contiguous allocation of subsequent
   clusters in each file when there are multiple writers.  This reduced
   internal fragmentation by a few percent, but it increased external
   fragmentation by up to a few thousand percent.
 
   Use simple sequential allocation instead.  Actually maintain the fsinfo
   sequence index for this.  The read and write of this index from/to
   disk still have many non-critical bugs, but we now write an index that
   has something to do with our allocations instead of being modified
   garbage.  If there is no fsinfo on the disk, then we maintain the index
   internally and don't go near the bugs for writing it.
 
   Allocating the first free cluster gives a layout that is almost as good
   (better in some cases), but takes too much CPU if the FAT is large and
   the first free cluster is not near the beginning.
 
   The effect of this change for untar and tar of a slightly reduced copy
   of /usr/src on a new file system was:
 
   Before (msdosfs 4K-clusters):
   untar:  459.57 real              untar from cached file (actually a pipe)
   tar:    342.50 real              tar from uncached tree to /dev/zero
   Before (ffs2 soft updates 4K-blocks 4K-frags)
   untar:   39.18 real
   tar:     29.94 real
   Before (ffs2 soft updates 16K-blocks 2K-frags)
   untar:   31.35 real
   tar:     18.30 real
 
   After (msdosfs 4K-clusters):
   untar    54.83 real
   tar      16.18 real
 
   All of these times can be improved further.
 
  VS> А экономия места будет за счёт меньшего количества инодов при большом
  VS> -i ?
 
 мне кажется это копейки.
 
  >> ну и случаи традиционного ньюсового спула и сквидового кэша мы не
  >> рассматриваем
 
  VS> Это понятно.
 
  VS> --
  VS> Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
  VS> 2:5005/49@fidonet http://vas.tomsk.ru/
  VS> --- ifmail v.2.15dev5.4
  VS>  * Origin: AO "Svyaztransneft", SibPTUS (2:5020/400)
 
 ... Компьютеры ненадежны, но люди еще ненадежнее
 --- GoldED+/BSD 1.1.5
  * Origin:  (2:5030/500)
 
 

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Тема:    Автор:    Дата:    newfs -i   Victor Sudakov   13 Sep 2007 11:03:04   newfs -i   Slawa Olhovchenkov   13 Sep 2007 11:29:36   Re: newfs -i   Victor Sudakov   13 Sep 2007 13:16:40   newfs -i   Slawa Olhovchenkov   13 Sep 2007 14:37:30   Re: newfs -i   Valentin Davydov   13 Sep 2007 14:33:25   Re: newfs -i   Victor Sudakov   14 Sep 2007 13:35:45   Re: newfs -i   Vadim Goncharov   14 Sep 2007 14:07:07   Re: newfs -i   Vadim Goncharov   13 Sep 2007 14:53:34