Date: Thu, 08 Dec 2005 17:16:07 +0900 From: Nate Lawson <nate@root.org> To: Scott Long <scottl@samsco.org> Cc: hackers@freebsd.org, Eric Anderson <anderson@centtech.com> Subject: Re: scsi-target and the buffer cache Message-ID: <4397EBC7.9030105@root.org> In-Reply-To: <4397B82C.5020004@samsco.org> References: <4395BF04.50101@centtech.com> <43960F55.3010508@root.org> <43975926.1010302@centtech.com> <43975F5F.5080901@samsco.org> <439782AA.6000408@root.org> <4397B731.6010308@centtech.com> <4397B82C.5020004@samsco.org>
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Scott Long wrote: > Eric Anderson wrote: > >> Nate Lawson wrote: >>> Agree 100%. While having it in usermode means there are boundary >>> crossings that increase per-transaction latency, the actual bulk data >>> transfer is via zero-copy IO and you should be able to exceed the >>> data transfer rates of several 10K RPM drives on decent hardware. >> >> Ok, great.. Now, will scsi_target work ok with raw devices, or only >> files? (although I'm not sure theres all that much difference really). >> > > You can write your userland code to use whatever files or devices you > want. Are you talking about the scs_target.c code in > /usr/share/examples? That's just a skeletal example that you can use > as a starting point for your own work. No, it's not just a skeletal example. You can point it at a raw device as the backing store file and it will work as a block device (i.e. RBC command set). It has been tested as working at least moderately fast over SCSI, FC, and firewire. -- Nate
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