On Feb 09 Chris Boot wrote:
> On 09/02/2012 14:30, Stefan Richter wrote:
> > World-wide uniqueness of this identification of an IEEE 1212 'unit'
> > comes from the combination of the 'unit's or 'node's EUI-64 and the
> > 'unit's 24 bits wide directory ID.
> >
> > Consistent with that, SAM-2...SAM-4 Annex A table A.2 says that SBP-3
> > target port identifiers are 11 bytes wide.
[...]
> Very interesting, I didn't realise this fully until you mentioned it. In
> fact SAM-3 says it's 11 bytes, and table A.3 says it's the concatenation
> of the EUI-64 with the 'Discovery ID', defined in IEEE-1212. I only
> looked briefly but I couldn't find any mention of the Discovery ID in
> IEEE-1212-2001. I didn't check SAM-2 or SAM-4.
SAM-2 says "Discovery ID"/ "See IEEE Std P1212...", SAM-4 says "Discovery
ID"/ "See ISO/IEC 13213:1994...". Perhaps it was indeed called Discovery
ID in one early P1212 version. Or perhaps a SAM editor mistyped it. There
is no such thing in ISO/IEC 13213 = IEEE 1212-1994 nor in IEEE 1212-2001.
> I just posted a commit to my github repo which does the following:
>
> 1. Maps SAM target ports to IEEE-1212 units.
> 2. Insists that a target port within the target framework is named using
> an EUI-64/GUID and exposes this in the IEEE-1212 unit directory's
> Unit_Unique_ID property.
So now we need to support unit unique ID in our initiator too.
> 3. Limits the SAM target port to only contain one TPG (target port
> group), which I believe only really make sense for iSCSI.
OK... So this is about multipathing, but not iSCSI specific in principle.
SAM allows a logical unit to be reached through more than one target port.
Building on that, SPC-3/-4 defines
- target port asymmetric access state: The characteristic that defines
the behavior of a target port and the allowable command set for a
logical unit when commands and task management functions are routed
through the target port maintaining that state,
- target port group: A set of target ports that are in the same target
port asymmetric access state at all times.
A logical unit which canbe reached through a whole bunch of target ports
can some of those ports into groups. Some details are specified in
SPC-3/-4 section 5.8 in a transport-agnostic manner. A transport
specification would certainly need to offer a mapping for all that.
SBP-2/-3 doesn't.
--
Stefan Richter
-=====-===-- --=- -=-=-
http://arcgraph.de/sr/
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