Date: Wed, 20 Aug 1997 00:32:51 -0700 (PDT) From: Simon Shapiro <Shimon@i-Connect.Net> To: Tom Samplonius <tom@sdf.com> Cc: scsi@FreeBSD.ORG, Curt Welch <curt@kcwc.com> Subject: Re: expected performance with DPT RAID-5... Message-ID: <XFMail.970820003251.Shimon@i-Connect.Net> In-Reply-To: <Pine.BSF.3.95q.970817195747.28679B-100000@misery.sdf.com>
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Hi Tom Samplonius; On 18-Aug-97 you wrote: ... > "cd" to one of the RAID-5 file systems and do a "dd if=/dev/zero > of=testfile bs=64k count=1000". That will create a file called > "testfile" > 64MB in length (64k x 1000), and tell you how long it took to write it. > > Then reboot (the only way I know of clearing the FreeBSD file cache, > and > the DPT cache), and do a "dd if=testfile bs=64k of=/dev/null" to read the > file back. If you unmount the filesystems and make sure no other process has any of the device open, the caches will be flushed. The O/S must do so in case of removable media. The DPT firmware flushes caches in response to ALLOW MEDIA REMOVAL which is issued by sd.c in response to a close call. > On the write test I get about 3500000 bps, and the write test about > 9200000 bps. These results don't seem very good too me. For a RAID-5? Your WRITE is a bit (40%?) slow. READ is about right. Remember, these are sequential tests. You may want to adjust the read-ahead cache if this is your typical load (some people enjoy transferring many zeros from and to the disk :-). If you want a random test, pick up form my system st.c. It will do random seeks and either read, write, or read-modify-write and tell you how badly the system behaves. An interesting variation is to run, say 256 dd's and 1024 st's. Then measure throughput for a given stream. While (or soon after) the test is run do: (cd /dev;./MAKEDEV dpt0) echo -n "dump softc" > /dev/dpt0 get_dpt /dev/dpt0 Then look at the output. Yes, I will write a manpage and a front-end to this pair. Right now read the source in sys/dev/dpt/dpt_control.c Will answer many of your questions. Simon
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