Date: Wed, 27 Aug 2003 03:26:17 -0700 From: Terry Lambert <tlambert2@mindspring.com> To: Maciej Freudenheim <fahren@student.uci.agh.edu.pl> Cc: freebsd-performance@freebsd.org Subject: Re: Tuning Postgresql on FreeBSD 5.1 Message-ID: <3F4C8749.8DA398E0@mindspring.com> References: <200308250929.32143.paul@pathiakis.com> <20030826104038.GA63155@piggie>
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Maciej Freudenheim wrote: > > issues (if for no other reason than UFS+softupdates). Linux has > > problems with memory over commit situations and file system integrity > > while still maintaining reasonable file system performance (ext2 is > > faster than ext3 by a wide margin, but ext2 is _not_ a reliable FS). > > Even heard of reiserfs or xfs? > I'm not going to start Linux advocacy here, but it's so funny for me > when somebody says 'leenoox sux, it has crappy filesystem' that i can't > leave it without reply :) He didn't say that. He said that it had problems with memory overcommit situations; most OS's do. FreeBSD has done a lot of work on graceful degradation (i.e. it doesn't crash when it runs out of memory and there's no more swap available). So it's you whose bringing that interpretation to the data. I haven't seen any reasonable benchmarks on ReiserFS or XFS vs. Ext2FS or Ext3FS that didn't involve sticking too many files in a single directory and actually measuring btree vs. linear directory entry layout instead of actual raw I/O performance. For most modern hardware, you never get CPU bound, so the real determining factor on raw I/O performance is almost always going to be raw disk I/O speed, and safe speed is going to be lower than the manufacturer benchmarks; some disks are "unsafe at any speed", to paraphrase Ralph Nader, because they cache when you tell them not to using the commands the manufacturer has stated actually work to tell them not to. Also, FYI, Postgress, unlike Postfix or qmail, doesn't dump a zillion files into the same directory so they can measure themselves against a situational benchmark; they are actually smart enough to port to the POSIX interface, and not depend on FS implementation-specific tricks to get their performance. If you wanted to join the XFS porting project, I'm sure they'd like the help. If you wanted to port ReiserFS, realize that software patents will probably prevent your work from being used in the U.S. or Japan, unless you could prove it to be non-infringing on the Novell D.O.W. patents. -- Terry
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