Date: Sun, 14 Apr 1996 20:24:03 -0500 (EST) From: "John S. Dyson" <toor@dyson.iquest.net> To: nash@mcs.com Cc: gpalmer@freebsd.org, hackers@freebsd.org Subject: Re: Unices are created equal, but... Message-ID: <199604150124.UAA00317@dyson.iquest.net> In-Reply-To: <199604142325.SAA04908@zen.nash.org> from "Alex Nash" at Apr 14, 96 06:25:45 pm
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> > > > FreeBSD on UFS: > > > 2770803 bytes/second for writing the file > > > 3908495 bytes/second for reading the file > > > > > > Linux on ext2fs: > > > 3220442 bytes/second for writing the file > > > 1950476 bytes/second for reading the file > > > > ^^^^^^^ > > > > Is that 2nd figure for reading the file right? Seems a bit dubious > > ... unless they're really doing something screwey, you should get > > higher speeds READING than writing ... > > It's correct. In fact, I just tried it 5 more times to be sure: > > 1907889 bytes/second > 1899594 bytes/second > 1900282 bytes/second > 1873795 bytes/second > 1898218 bytes/second > > The write speed hovered around 3.2MB/s as before. > > I admit it's strange, but I also saw this on a P100 with an Adaptec > 2940. The reads would be (somewhere in the neighborhood of) 800K/s > slower than the writes. After installing FreeBSD on that system, > the reads and writes fell within 100K/s of each other. > > Alex > It appears that Linux is depending upon the drive for read-ahead. FreeBSD has an algorithm that depends relatively less on drive caching. Of course, that is becoming less and less necessary. It is likely that the drive read caching has been disabled? John dyson@freebsd.org
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