Date: Wed, 23 Feb 2000 19:46:36 +0100 From: Brad Knowles <blk@skynet.be> To: freebsd-stable@freebsd.org Subject: Multiple Adaptec 2940U2W controllers? Message-ID: <v0422081fb4d9d7f862b6@[195.238.1.121]>
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Folks, I've got a machine I'm working on, and I'm seeing some unusual problems, so I wanted to get a sanity check. The machine in question is a Dell 1300 with two 450Mhz processors (512KB L2 cache each) and 1GB ECC RAM. In addition to the on-board Adaptec AIC-7890 controller (to which the system disk is attached, a Quantum Atlas IV 9GB), I have two Adaptec 2940U2W controllers. Each of these two controllers is attached to a different interface on a Hitachi/Comparex D1400 mainframe-style refrigerator-size drive array, with twenty 18GB Seagate 10kRPM "Cheetah" disks (plus one hot spare not currently being used) spread across five internal SCSI channels, and with 1GB ECC battery backed-up write-back cache (mirrored between the two controllers, so effective size is halved). On this machine, I have installed FreeBSD 3.4-STABLE (I cvsup'ed late last week, so it should be fairly up-to-date). Needless to say, we would expect this system to pretty much scream at disk I/O. Of course, this is precisely what it is not doing. Fortunately, all the work I have been doing over the last few days is in preparation for a Hitachi/Comparex performance expert to come in tomorrow and help us tune this thing for maximum performance from their perspective, but I'm seeing something weird from the host side and I'd like to ask if anyone else has seen anything similar. In particular, when we run the "postmark" benchmark on a single filesystem, we get some decent results (although not nearly as good as we'd like). When we run the same benchmark on two different filesystems mounted through two different controllers, well, performance really goes into the toilet -- the result is about 1/10th as fast as the single filesystem test. But, when we test the same two filesystems mounted through the same Adaptec controller, we see each test get almost exactly half the performance of the single filesystem test. This just doesn't make any sense to me. If anything, I would expect the dual controller configuration to result in each postmark benchmark getting nearly as much throughput as the single filesystem test, so that the aggregate is almost twice as much. But instead, it's ten times as slow?!? This just boggles my mind, and I don't have the first clue where to go looking to see what the problem might be. Is there any additional information I could provide that might prove helpful? Could there be conflicts of some sort between the two Adaptec 2940U2W controllers? Thanks for any and all advice, observations, and assistance you can provide! -- These are my opinions and should not be taken as official Skynet policy _________________________________________________________________________ |o| Brad Knowles, <blk@skynet.be> Belgacom Skynet NV/SA |o| |o| Systems Architect, Mail/News/FTP/Proxy Admin Rue Col. Bourg, 124 |o| |o| Phone/Fax: +32-2-706.13.11/726.93.11 B-1140 Brussels |o| |o| http://www.skynet.be Belgium |o| \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/ Unix is like a wigwam -- no Gates, no Windows, and an Apache inside. Unix is very user-friendly. It's just picky who its friends are. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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