Date: Sat, 30 Nov 1996 12:57:43 -0100 From: Darius Moos <moos@degnet.baynet.de> To: "John S. Dyson" <toor@dyson.iquest.net> Cc: mango@staff.communique.net, hackers@freefall.freebsd.org, hardware@freefall.freebsd.org Subject: Re: Adaptec UW controller and Seagate Elite performance ? Message-ID: <32A03D57.6274@degnet.baynet.de> References: <199611300444.XAA09675@dyson.iquest.net>
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One thing that stroke me some time ago was the termination of the SCSI-bus. After changing from passive to active termination, the speed of my disks doubled !!! Darius Moos. John S. Dyson wrote: > > > > > # bonnie -s 40 (akira, http running) > > -------Sequential Output-------- ---Sequential Input-- --Random-- > > -Per Char- --Block--- -Rewrite-- -Per Char- --Block--- --Seeks--- > > MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec %CPU > > 40 3271 34.8 3085 13.0 1559 8.3 10330 97.1 44763 95.7 991.0 20.4 > > > > and > > IOZONE performance measurements: > > 2039008 bytes/second for writing the file > > 34861747 bytes/second for reading the file > > > > It bothered me that: > > 1- reading is 20 times faster than writing > > You are seeing the results of caching. The system remembers what > is written so that it doesn't have to unnecessarily re-read the > data. > > > > > 2- 2Mbytes/s for writing seems slow, even if this was a scsi-2 and not > > an > > scsi fast and wide drive. > > > I don't know why your iozone write perf is so slow, unless you are writing > 512 bytes at a time. Note also, that you might not have the write > behind caching enabled on your drive. > > Try the following commands: > > # iozone auto > and > # iozone 40 8192 > and > # iozone <size-of-memory*2> 8192 > > and let me know the results. > > John > dyson@freebsd.org
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