Date: Mon, 14 Sep 1998 12:38:54 -0500 (CDT) From: Joel Ray Holveck <joelh@gnu.org> To: Terry Lambert <tlambert@primenet.com> Cc: tom@uniserve.com (Tom), gpalmer@FreeBSD.ORG, irc@cooltime.simplenet.com, freebsd-current@FreeBSD.ORG Subject: Re: Download of FreeBSD 3.0-SNAP Message-ID: <199809141738.MAA08622@detlev.UUCP> In-Reply-To: <199809132343.QAA23937@usr04.primenet.com> References: <199809132343.QAA23937@usr04.primenet.com>
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> While this is fine for disks that can support multiple outstanding > commands pending simultaneously (giving them something to sort), > it is less of a good idea for stupid disks that must be sent > commands serially. Like, oh, say, E/IDE disks. > The FreeBSD E/IDE driver supports queued tagged commands, but > few E/IDE drives have this capability (in fact, I am not aware > of *any* that support this portion of the spec.). > It should be noted that some SCSI devices don't support tagged > command queuing, either (but we don't buy those, since they are > in the minority). I'm no disk expert, so please tell me: what is tagged command queueing? Is it the ability to have multiple outstanding requests, with the device reordering the requests for optimal efficiency, and relying on a cookie in the header to differentiate between requests? Best, joelh -- Joel Ray Holveck - joelh@gnu.org - http://www.wp.com/piquan Fourth law of programming: Anything that can go wrong wi sendmail: segmentation violation - core dumped To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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