[Bug 204929] fs_optim and fs_minfree default value is 10% in man fs(5),while newfs(8),tunefs(8) is 8%

[bugzilla-noreply]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204929

--- Comment #1 from Jov  ---
from the tunefs -p,the 8% is correct：

root@:~ # tunefs -p /dev/da0p2
tunefs: POSIX.1e ACLs: (-a)disabled
tunefs: NFSv4 ACLs: (-N)   disabled
tunefs: MAC multilabel: (-l)   disabled
tunefs: soft updates: (-n) enabled
tunefs: soft update journaling: (-j)   enabled
tunefs: gjournal: (-J) disabled
tunefs: trim: (-t) disabled
tunefs: maximum blocks per file in a cylinder group: (-e)  4096
tunefs: average file size: (-f)16384
tunefs: average number of files in a directory: (-s)   64
tunefs: minimum percentage of free space: (-m) 8%
tunefs: space to hold for metadata blocks: (-k)6408
tunefs: optimization preference: (-o)  time
tunefs: volume label: (-L)

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[Bug 204929] fs_optim and fs_minfree default value is 10% in man fs(5),while newfs(8),tunefs(8) is 8%

[bugzilla-noreply]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=204929

Bug ID: 204929
   Summary: fs_optim and fs_minfree default value is 10% in man
fs(5),while newfs(8),tunefs(8) is 8%
   Product: Documentation
   Version: Latest
  Hardware: amd64
OS: Any
Status: New
  Severity: Affects Some People
  Priority: ---
 Component: Documentation
  Assignee: freebsd-doc@FreeBSD.org
  Reporter: am...@amutu.com

this from fs(5):
The fs_minfree element gives the minimum acceptable percentage of file
 system blocks that may be free.  If the freelist drops below this level
 only the super-user may continue to allocate blocks.  The fs_minfree ele‐
 ment may be set to 0 if no reserve of free blocks is deemed necessary,
 however severe performance degradations will be observed if the file sys‐
 tem is run at greater than 90% full; thus the default value of fs_minfree
 is 10%.

The element fs_optim specifies whether the file system should try to min‐
 imize the time spent allocating blocks, or if it should attempt to mini‐
 mize the space fragmentation on the disk.  If the value of fs_minfree
 (see above) is less than 10%, then the file system defaults to optimizing
 for space to avoid running out of full sized blocks.  If the value of
 minfree is greater than or equal to 10%, fragmentation is unlikely to be
 problematical, and the file system defaults to optimizing for time.


this from newfs(8):
 -m free-space
 The percentage of space reserved from normal users; the minimum
 free space threshold.  The default value used is defined by
 MINFREE from , currently 8%.  See tunefs(8) for
 more details on how to set this option.

-o optimization
 (space or time).  The file system can either be instructed to try
 to minimize the time spent allocating blocks, or to try to mini‐
 mize the space fragmentation on the disk.  If the value of min‐
 free (see above) is less than 8%, the default is to optimize for
 space; if the value of minfree is greater than or equal to 8%,
 the default is to optimize for time.  See tunefs(8) for more
 details on how to set this option.

this from tunefs:
 -m minfree
 Specify the percentage of space held back from normal users; the
 minimum free space threshold.  The default value used is 8%.
 Note that lowering the threshold can adversely affect perfor‐
 mance:

 ·   Settings of 5% and less force space optimization to always be
 used which will greatly increase the overhead for file
 writes.

 ·   The file system's ability to avoid fragmentation will be
 reduced when the total free space, including the reserve,
 drops below 15%.  As free space approaches zero, throughput
 can degrade by up to a factor of three over the performance
 obtained at a 10% threshold.

 If the value is raised above the current usage level, users will
 be unable to allocate files until enough files have been deleted
 to get under the higher threshold.

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