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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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