Date: Sat, 17 Sep 2005 00:19:09 -0700 From: Ade Lovett <ade@freebsd.org> To: Scott Long <scottl@samsco.org> Cc: freebsd-scsi@freebsd.org Subject: Re: CAM tags / reset problem Message-ID: <8A5A248D-7529-4EE7-A7B7-4CB81C3ABDDB@freebsd.org> In-Reply-To: <432BC20B.2090603@samsco.org> References: <3A1FD217-5880-4845-9F64-5DD9395D1C6D@FreeBSD.org> <432BC20B.2090603@samsco.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sep 17, 2005, at 00:13 , Scott Long wrote: > It's a bit late tonight for me to think coherently about this and give > the patch a good review, but I promise that it will happen. Maybe > Justin, Ken, Matt, or Nate can also step in and look at it. Are > you saying that there are multiple bus resets happening in > relatively quick > succession on each bus during the inital probe? Are you observing > this > with only a particular controller family, or with multiple ones? This is fallout from the well-documented issues with multiple Seagate drives on an Adaptec 39320 controller: ahd0: <Adaptec 39320A Ultra320 SCSI adapter> port 0x3400-0x34ff, 0x3000-0x30ff me m 0xfc200000-0xfc201fff irq 48 at device 1.0 on pci2 ahd0: [GIANT-LOCKED] aic7902: Ultra320 Wide Channel A, SCSI Id=7, PCI-X 101-133Mhz, 512 SCBs After the recent nswbuf patch, we were still noticing anomalies with performance on the chain. This is certainly a degenerate case (Seagate drives on a U320 chain), but as far as I can tell it applies to any set of controller/disk pairs should multiple bus resets occur on startup. I've got another test box with Hitachi drives (same controller) and am trying to figure out a way to engineer a set of events that would cause such multiple resets but have as yet been unsuccessful. However, with this patch, we now have chains of 7/8 Seagate drives running at U320 with overall bus throughput around 312MBps. Prior to this, on random read/writes, we were observing less than 100MBps. It definitely merits looking at to see if it breaks anything elsewhere (particularly with "well-behaved" SCSI controller/disk combinations), hence the request for review. -aDe
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?8A5A248D-7529-4EE7-A7B7-4CB81C3ABDDB>