Date: Wed, 01 Nov 2000 21:57:40 -0700 From: "Justin T. Gibbs" <gibbs@scsiguy.com> To: The Hermit Hacker <scrappy@hub.org> Cc: Tom Samplonius <tom@sdf.com>, freebsd-scsi@FreeBSD.ORG Subject: Re: iostat: tps for SCSI drives ... Message-ID: <200011020457.eA24vea67590@aslan.scsiguy.com> In-Reply-To: Your message of "Wed, 01 Nov 2000 18:43:55 -0400." <Pine.BSF.4.21.0011011840510.494-100000@thelab.hub.org>
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>> Maxtags is the limit imposed by the quirk entry matching the device. > >Okay, under what conditions would dev_openings == maxtags? My best drive >that I can find on my various machines is a brand new LVD drive: You will only see this very early in the boot process before a device indicates that it cannot handle "maxtags" via a queue full or if you have a device that can really achieve "maxtags". For instance, some RAID arrays can perform the full 256 tags that can be outstanding is SCSI-2, but most drives max out at 64 or 63 tags. Only recently have I found some IBM drives that will support 128 tags. That said, the system will only allocate resources to support the number of transactions it is determined a device can use. The "maxtags" value is just an upper bound. -- Justin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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