Date: Mon, 19 Aug 2002 01:55:10 +0200 (CEST) From: =?ISO-8859-1?Q?G=E9rard_Roudier?= <groudier@free.fr> To: "Kenneth D. Merry" <ken@kdm.org> Cc: Sergey Babkin <babkin@bellatlantic.net>, "Semen A. Ustimenko" <semenu@FreeBSD.ORG>, <freebsd-hackers@FreeBSD.ORG>, <freebsd-scsi@FreeBSD.ORG> Subject: Re: SCSI device emulation using SCSI host controller Message-ID: <20020819012514.C200-100000@localhost.my.domain> In-Reply-To: <20020813203037.A53640@panzer.kdm.org>
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On Tue, 13 Aug 2002, Kenneth D. Merry wrote: > On Tue, Aug 13, 2002 at 21:12:59 -0400, Sergey Babkin wrote: > > "Kenneth D. Merry" wrote: > > > > > > On Tue, Aug 13, 2002 at 23:41:14 +0700, Semen A. Ustimenko wrote: > > > > Hi! > > > > > > > > I beg you all pardon for a question not related directly to FreeBSD= , but > > > > if the answer is ``yes'', then I believe FreeBSD will be in deal. > > > > > > > > The question is: "Can I emulate a SCSI device (tape, if that matter= s) > > > > using usual SCSI host controller and specific software, or I will > > > > definitely need specific hardware?" > > > > > > You'll need either the right Adaptec or QLogic controller, but yes, i= t can > > > be done with FreeBSD. > > > > Or Symbios (now LSI Logic). > > Has anyone done any target mode code for their boards? > > I know they're probably capable of it, but AFAIK, the sym(4) driver doesn= 't > support target mode and I didn't see anything in the mpt(4) commit that > indicated that it supports target mode either. Indeed sym(4) doesn't support target mode. I had such plan to add such support a couple of years ago in order to make possible some low cost high speed host-to-host communication, but finally I didn't found for now good reasons enough for completing this work. Instead, the result would have not high speed at high cost communication and probably bunches of undocumented hardware bugs to suffer of. Btw, I haven't any project related to SCSI device emulation. My impressions and observations about Ncr/Symbios/Lsi 8xx/1010 SCSI/SCRIPT based devices for SCSI target mode are the following: 1) The older the chip, the better for target mode :-) (I mean less hardware bugs to work-around) 2) The vendor of the chips don't provide target mode drivers nor encourage this much to develop such. 3) Given the Device Errata Listings I could look into, the Ultra-160 LSI1010-33 is only usable in asynchronous mode (about 3 Mega-transfers per second) in target mode. (Better not to want to support target mode on those chips) Given #3, the maximum throughput with target mode on such chip family cannot be greater that 80 MB/s which is not faster than Gigabit ethernet for example. The current LSILOGIC interface technology for SCSI chip is MPT/fusion. I would suggest to rather invest on it. The 8xx SCSI scripts based technology will never support more than Ultra-160. G=E9rard. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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