Date: Wed, 17 Jul 2002 11:36:31 -0700 From: Brooks Davis <brooks@one-eyed-alien.net> To: Dave Hayes <dave@jetcafe.org> Cc: Andrew Heybey <ath@niksun.com>, freebsd-scsi@FreeBSD.ORG Subject: Re: Random hangs on (at least) SCSI reads Message-ID: <20020717113631.A30914@Odin.AC.HMC.Edu> In-Reply-To: <200207171826.g6HIQr049869@hokkshideh2.jetcafe.org>; from dave@jetcafe.org on Wed, Jul 17, 2002 at 11:26:48AM -0700 References: <200207171826.g6HIQr049869@hokkshideh2.jetcafe.org>
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[-- Attachment #1 --] On Wed, Jul 17, 2002 at 11:26:48AM -0700, Dave Hayes wrote: > Well we've isolated the problem (we think). These machines are built > using a 2U case. This requires a PCI riser card that plugs into the > motherboard PCI slot and provides horizontal (rather than vertical) > card mounting options. > > With that riser card out, I've run the same "crashme" script which > puts a moderate to heavy load on the disk subsystem, and the machine > is still up (16 hours and counting). > > Electronically speaking that riser card adds a extra capacitance and > resistance that is probably not in the design spec for PCI. That's > the current theory anyway. I don't know enough about PCI to know > if that makes sense or not. I do know we are going to try slowing > down the SCSI transfer speed to see if that helps any. I'd bet a lot more of a bum riser card then on a generic problem with riser cards. We've got got quite a few 2U systems running various cards with few problems. The only problem we've seen with a SCSI card was a RAID control that got fried when we power cycled a hung system. One other possiablity to consider is lack of decent air flow causing heating problems. If you run without a riser card, the system has to be open which would improve air flow around passivly cooled components. -- Brooks -- Any statement of the form "X is the one, true Y" is FALSE. PGP fingerprint 655D 519C 26A7 82E7 2529 9BF0 5D8E 8BE9 F238 1AD4 [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE9NbkuXY6L6fI4GtQRAuJXAJkBQALt/A3OD/xzdzPfri/OZH0xZACeKt9v 2JtTB/N6V6iltc7MlNMi0ts= =QQVi -----END PGP SIGNATURE-----
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