David, your question surprises me a lot. From where have you decided that SCST supports only pass-through backstorage? Does the RAM disk, which Bart has been using for performance tests, look like a SCSI device?2. I think, everybody will agree that Linux iSCSI target should work over some standard SCSI target framework. Hence the choice gets narrower: SCST vs STGT. I don't think there's a way for a dedicated iSCSI target (i.e. PyX/LIO) in the mainline, because of a lot of code duplication. Nicholas could decide to move to either existing framework (although, frankly, I don't think there's a possibility for in-kernel iSCSI target and user space SCSI target framework) and if he decide to go with SCST, I'll be glad to offer my help and support and wouldn't care if LIO-SCST eventually replaced iSCSI-SCST. The better one should win.
why should linux as an iSCSI target be limited to passthrough to a SCSI device.
the most common use of this sort of thing that I would see is to load up a bunch of 1TB SATA drives in a commodity PC, run software RAID, and then export the resulting volume to other servers via iSCSI. not a 'real' SCSI device in sight.