Name that multi-port SCSI device

Gene_Milligan at notes.seagate.com Gene_Milligan at notes.seagate.com
Sun May 30 08:21:24 PDT 1999


* From the T10 Reflector (t10 at symbios.com), posted by:
* Gene_Milligan at notes.seagate.com
*
<<The ports were parallel SCSI.  Using my example a BUS RESET occurred on
port
A, causing LU X to experience a LU reset.  In order to let the host
attached
to port B know that LU X was reset, LU X reported a POR Unit Attention
condition to all initiator attached to Port B.  The POR Unit Attention
Condition causes port B to reset it's negotiated data transfer parameters
for all hosts.  Now a host attached to port B with outstanding I/O to LU Y
will have a mismatch in data transfer parameters unless LU Y does something
like also reporting POR Unit Attention.>>

     Host systems did not agree on how they wanted reset to operate with
dual ported drives. Consequently a mode page control was used to define
which way reset on a port functioned. This was part of the dual port SCSI
definition that was in earlier drafts and later removed to still the debate
over whether the definition should be KISS dual port or ultimate
multipathing.

Gene



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