Date: Tue, 01 Dec 2015 07:51:31 +0000 From: bugzilla-noreply@freebsd.org To: freebsd-doc@FreeBSD.org Subject: [Bug 204929] fs_optim and fs_minfree default value is 10% in man fs(5),while newfs(8),tunefs(8) is 8% Message-ID: <bug-204929-9@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D204929 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: amutu@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 e= le=E2=80=90 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 s= ys=E2=80=90 tem is run at greater than 90% full; thus the default value of fs_minf= ree is 10%. The element fs_optim specifies whether the file system should try to min=E2= =80=90 imize the time spent allocating blocks, or if it should attempt to min= i=E2=80=90 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 optimiz= ing 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 <ufs/ffs/fs.h>, 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 min= i=E2=80=90 mize the space fragmentation on the disk. If the value of min= =E2=80=90 free (see above) is less than 8%, the default is to optimize f= or 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; t= he minimum free space threshold. The default value used is 8%. Note that lowering the threshold can adversely affect perfor= =E2=80=90 mance: =C2=B7 Settings of 5% and less force space optimization to a= lways be used which will greatly increase the overhead for file writes. =C2=B7 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 wi= ll be unable to allocate files until enough files have been delet= ed to get under the higher threshold. --=20 You are receiving this mail because: You are the assignee for the bug.=
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