f_campbell at qlc.com
Mon Feb 24 13:43:17 PST 1997
* From the SCSI Reflector (scsi at symbios.com), posted by:
* Frank Campbell <f_campbell at qlc.com>
Before we consider withdrawal of SBP we should subject SBP-2 to greater
There are aspects of SBP-2 which I believe should give rise to concern:
1. SBP-2 requires that targets deal with scatter/gather and paging
issues within the host.
2. SBP-2 requires that targets have the capability to break transfers up
on odd byte boundaries.
3. SBP-2 uses host addresses as handles with no means of identifying
stale handles, exposing the risk of stale handles causing corruption.
4. SBP-2 uses more bus transactions than necessary to perform I/O. As a
worst case example, a single sector read from disk requires up to 14 bus
arbitration cycles and 14 packet transfers.
5. SBP-2 hosts use DMA addresses supplied by targets, creating security
Items 1,2 and 4 relate to the cost and complexity of target hardware and
firmware. Items 3 and 5 relate to reliability and security.
Costa Mesa, California.
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