Date: Mon, 10 Dec 2001 09:41:49 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: Sheldon Hearn <sheldonh@starjuice.net> Cc: Kirk McKusick <mckusick@mckusick.com>, freebsd-arch@FreeBSD.ORG Subject: Re: Using a larger block size on large filesystems Message-ID: <200112101741.fBAHfnB47140@apollo.backplane.com> References: <53392.1007976918@axl.seasidesoftware.co.za>
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Looks good to me!
-Matt
:On Fri, 07 Dec 2001 11:12:57 PST, Kirk McKusick wrote:
:
:> FYA, we had this same debate a bit over a decade ago when we changed
:> the default from 4K/512 to 8K/1K. Obviously, we decided not to
:> special case small filesystems then despite great hand-wringing over
:> what would happen...
:
:Thanks. This takes a load off my shoulders with respect to our tendency
:to repeat our mistakes in ignorance of our history. :-)
:
:Here's what I intend to commit.
:
:Ciao,
:Sheldon.
:
:Index: share/man/man7/tuning.7
:===================================================================
:RCS file: /home/ncvs/src/share/man/man7/tuning.7,v
:retrieving revision 1.29
:diff -u -d -r1.29 tuning.7
:--- share/man/man7/tuning.7 7 Dec 2001 18:17:37 -0000 1.29
:+++ share/man/man7/tuning.7 10 Dec 2001 09:23:48 -0000
:@@ -199,19 +199,29 @@
: .Pp
: .Fx
: performs best when using 8K or 16K filesystem block sizes.
:-The default filesystem block size is 8K.
:-For larger partitions it is usually a good
:-idea to use a 16K block size.
:-This also requires you to specify a larger
:+The default filesystem block size is 16K,
:+which provides best performance for most applications,
:+with the exception of those that perform random access on large files
:+(such as database server software).
:+Such applications tend to perform better with a smaller block size,
:+although modern disk characteristics are such that the performance
:+gain from using a smaller block size may not be worth consideration.
:+Using a block size larger than 16K
:+can cause fragmentation of the buffer cache and
:+lead to lower performance.
:+.Pp
:+The defaults may be unsuitable
:+for a filesystem that requires a very large number of inodes
:+or is intended to hold a large number of very small files.
:+Such a filesystem should be created with an 8K or 4K block size.
:+This also requires you to specify a smaller
: fragment size.
: We recommend always using a fragment size that is 1/8
: the block size (less testing has been done on other fragment size factors).
: The
: .Xr newfs 8
: options for this would be
:-.Dq Li "newfs -f 2048 -b 16384 ..." .
:-Using a larger block size can cause fragmentation of the buffer cache and
:-lead to lower performance.
:+.Dq Li "newfs -f 1024 -b 8192 ..." .
: .Pp
: If a large partition is intended to be used to hold fewer, larger files, such
: as a database files, you can increase the
:Index: sbin/newfs/newfs.8
:===================================================================
:RCS file: /home/ncvs/src/sbin/newfs/newfs.8,v
:retrieving revision 1.47
:diff -u -d -r1.47 newfs.8
:--- sbin/newfs/newfs.8 7 Dec 2001 13:18:28 -0000 1.47
:+++ sbin/newfs/newfs.8 10 Dec 2001 09:11:49 -0000
:@@ -110,7 +110,7 @@
: for more details on how to set this option.
: .It Fl b Ar block-size
: The block size of the file system, in bytes. It must be a power of 2. The
:-default size is 8192 bytes, and the smallest allowable size is 4096 bytes.
:+default size is 16384 bytes, and the smallest allowable size is 4096 bytes.
: The optimal block:fragment ratio is 8:1.
: Other ratios are possible, but are not recommended,
: and may produce unpredictable results.
:@@ -141,7 +141,7 @@
: .Ar blocksize Ns /8
: and
: .Ar blocksize .
:-The default is 1024 bytes.
:+The default is 2048 bytes.
: .It Fl g Ar avgfilesize
: The expected average file size for the file system.
: .It Fl h Ar avgfpdir
:@@ -271,15 +271,19 @@
: bad sector allocation.
: .El
: .Sh EXAMPLES
:-.Dl newfs -b 16384 -f 2048 /dev/ad3s1a
:+.Dl newfs /dev/ad3s1a
: .Pp
: Creates a new ufs file system on
: .Pa ad3s1a .
: .Nm
: will use a block size of 16384 bytes, a fragment size of 2048 bytes
: and the largest possible number of cylinders per group.
:-These values tend to produce better performance than the defaults
:-for most applications.
:+These values tend to produce better performance for most applications
:+than the historical defaults
:+(8192 byte block size and 1024 byte fragment size).
:+This large fragment size
:+may lead to large amounts of wasted space
:+on filesystems that contain a large number of small files.
: .Sh SEE ALSO
: .Xr fdformat 1 ,
: .Xr disktab 5 ,
:Index: sbin/newfs/newfs.c
:===================================================================
:RCS file: /home/ncvs/src/sbin/newfs/newfs.c,v
:retrieving revision 1.45
:diff -u -d -r1.45 newfs.c
:--- sbin/newfs/newfs.c 3 Nov 2001 08:35:11 -0000 1.45
:+++ sbin/newfs/newfs.c 7 Dec 2001 15:09:18 -0000
:@@ -98,8 +98,8 @@
: * sectorsize <= DESFRAGSIZE <= DESBLKSIZE
: * DESBLKSIZE / DESFRAGSIZE <= 8
: */
:-#define DFL_FRAGSIZE 1024
:-#define DFL_BLKSIZE 8192
:+#define DFL_FRAGSIZE 2048
:+#define DFL_BLKSIZE 16384
:
: /*
: * Cylinder groups may have up to many cylinders. The actual
:Index: usr.sbin/sysinstall/install.c
:===================================================================
:RCS file: /home/ncvs/src/usr.sbin/sysinstall/install.c,v
:retrieving revision 1.312
:diff -u -d -r1.312 install.c
:--- usr.sbin/sysinstall/install.c 9 Dec 2001 09:47:09 -0000 1.312
:+++ usr.sbin/sysinstall/install.c 10 Dec 2001 00:20:21 -0000
:@@ -1121,7 +1121,7 @@
: variable_set2(SYSTEM_STATE, "update", 0);
: else
: variable_set2(SYSTEM_STATE, "init", 0);
:- variable_set2(VAR_NEWFS_ARGS, "-b 8192 -f 1024", 0);
:+ variable_set2(VAR_NEWFS_ARGS, "", 0);
: variable_set2(VAR_CONSTERM, "NO", 0);
: return DITEM_SUCCESS;
: }
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