Date: Mon, 16 Jul 2001 08:00:42 -0700 From: Nick Sayer <nsayer@quack.kfu.com> To: Lamont Granquist <lamont@scriptkiddie.org> Cc: Bruce Burden <brucegb@realtime.net>, freebsd-stable@FreeBSD.ORG Subject: Re: Regarding New FreeBSD BenchMark From Sysadmin Mag (left out a fiew tuning options) Message-ID: <3B53019A.5080902@quack.kfu.com> References: <20010713235530.W12542-100000@coredump.scriptkiddie.org>
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Lamont Granquist wrote: > i've got: > > ahc0: <Adaptec 3960D Ultra160 SCSI adapter> port 0xcc00-0xccff mem 0xefffe000-0xefffefff irq 11 at device 13.0 on pci0 > aic7899: Wide Channel A, SCSI Id=7, 32/255 SCBs > ahc1: <Adaptec 3960D Ultra160 SCSI adapter> port 0xdc00-0xdcff mem 0xeffff000-0xefffffff irq 10 at device 13.1 on pci0 > aic7899: Wide Channel B, SCSI Id=7, 32/255 SCBs > > and: > > da0 at ahc0 bus 0 target 0 lun 0 > da0: <SEAGATE ST336704LW 0004> Fixed Direct Access SCSI-3 device > da0: 160.000MB/s transfers (80.000MHz, offset 63, 16bit), Tagged Queueing Enabled > da0: 35003MB (71687369 512 byte sectors: 255H 63S/T 4462C) > > and WCE was = 1 by default, but camcontrol worked to turn it off > I could be wrong, but my understanding is that tag queueing is a form of write caching, but all it does is allow the drive to reorder the writes. Unlike the evil form of write caching, the OS is given true completion notice, which is what makes it OK. So if you have tag queueing, you should leave write caching on. This is only possible on SCSI drives and certain very new IBM ATA disks. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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