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SubjectRe: Linux as a SCSI _Target_ device?
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On Wed, 11 Nov 1998, MOLNAR Ingo wrote:

<SNIP>
> On Tue, 10 Nov 1998, Jeff Noxon wrote:
> > Can anyone tell me if it would be possible to make a Linux system appear
> > to another system as a SCSI target? I want to RAID 5 a whole mess of
> > IDE drives and have it appear to another Linux box as a SCSI hard drive.
> > I'm guessing it would be possible with one of the Symbios chips and some
> > clever hacking. True/False? Where to start?
> >
> > If I need special hardware, I'm out.
>
> i'm not sure wether such a thing exists in retail, but you also need
> kernel support for this. The point would be to 'export' a block device
> (RAID5) as an SCSI target.
>

except for the support for scsi target mode on the controller everything
else could be done (a little slower) in user space.

we would need the following

1. configuration/management commands (what are you, reformat yourself,
etc)

2. read/write request support, this could simply map a block number (from
the host system) to a spot on a local filesystem

putting this in the kernel would be like NFS, a good speed boost, but not
nessasary to function.

David Lang


> i was thinking about this one yes, this way Linux could be a real
> hardware-RAID box. It's _not_ really complex, but i havent seen this yet.
> The board has to do something like this:
>
> - send an IRQ if an SCSI command arrives
> - should be able to DMA out to the SCSI bus and also accept DMA
> transfers.
>
> probably there are some RT considerations (Linux has to react within a
> given timeframe), but maybe not, and Linux can sure can do much better
> than the millisec-timescale of RAID arrays. It is an interesting project.
> True 50-500G hardware-RAID for $5K or so.
>
> -- mingo
>
>
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> Please read the FAQ at http://www.tux.org/lkml/
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