Time to write routing tables

Hugh Curley hcurley at indra.com
Thu Feb 27 02:45:34 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Hugh Curley" <hcurley at indra.com>
*
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If I understand the protocol correctly, when the domain powers on (or
when one or more devices are added), all the initiators will discover
the entire topology by using Discovery one phy at a time.  All
initiators will then write the complete routing table for each expander
that has a configurable routing table. =20
=20
Changing the standard from "all initiators shall discover and write the
routing table" to "all initiators should discover and write the routing
table" simply means that in some configurations will have no initiators
that do this, while in other configurations all initiators will still =
do
it.  When I purchase the equipment for my new SAS domain, I will
probably by all the initiators from the same vendor.  If brand X writes
the routing table, then all my initiators will attempt to do so.  If
brand Y does not write the routing table, then none of my initiators
will attempt to do so.
=20
Let us imagine a domain that uses only 8% of the total possible
connections; consisting of 100 initiators and 900 targets.  How long
will it take to do discovery and update the routing tables.
=20
Would it not be quicker if a single initiator was selected to create =
the
tables?  It could be the one with the highest SAS address, lowest SAS
address, or the first one there marks the table unconfigurable, or
places a reserve (similar to the SCSI Reserve) on the SMP target.
=20
Am I on target?
=20
Thanks,
=20
Hugh Curley
hcurley at indra.com =20
=20

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 If I understand the protocol = correctly, when the=20 domain powers on (or when one or more devices are added), all the = initiators=20 will discover the entire topology by using Discovery one phy at a = time. =20 All initiators will then write the complete routing table for each = expander that=20 has a configurable routing table.  
 
 Changing the standard from "all initiators shall discover and = write=20 the routing table" to "all initiators should discover and write=20 the routing table" simply means that in some configurations will = have no=20 initiators that do this, while in other configurations all initiators = will still=20 do it.  When I purchase the equipment for my new SAS domain, I = will=20 probably by all the initiators from the same vendor.  If brand X = writes=20 the routing table, then all my initiators will attempt to do = so.  If=20 brand Y does not write the routing table, then none of my initiators = will=20 attempt to do so.
  
 Let us imagine a domain that uses only = 8% of the=20 total possible connections; consisting of 100 initiators and 900 = targets. =20 How long will it take to do discovery and update the routing=20 tables.
  
 Would it not be quicker if a single = initiator was=20 selected to create the tables?  It could be the one with the = highest SAS=20 address, lowest SAS address, or the first one there marks the table=20 unconfigurable, or places a reserve (similar to the SCSI Reserve) on = the SMP=20 target.
  
 Am I on target?
  
 Thanks,
  
 Hugh Curley
 hcurley at indra.com
  



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