multi-path IO in SCSI mid-layer

From: Patrick Mansfield (
Date: Tue Jun 26 2001 - 13:00:40 EST

Hi -

I'm interested in multi-path IO in the linux scsi mid-layer.

Are there developers working on changes to the scsi layers/interfaces?
I've seen references about such work, but no details.

Anyone else interested in or working on multi-path IO in the mid-layer?

I've looked at the code as to what changes might be required, and did
a simple prototype to issue IO requests using multiple paths for one device -
configuring one device in with multiple paths using SCSI INQUIRY page 0x83,
and selecting a path (just round-robin) at scsi_submit_cmd() time.

But, a decent multi-path IO implementation requires significant changes
to the current linux scsi interfaces/structures - especially where no
functional interfaces exist, such as the direct references to Scsi_Device
host, and Scsi_Host host_queue.

Patrick Mansfield
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