SAS: XFER_RDY - CREDIT_BLOCKED - Resuming Data Transfer

Bellamy, Wayne wayne.bellamy at
Thu Mar 11 12:56:58 PST 2004

* From the T10 Reflector (t10 at, posted by:
* "Bellamy, Wayne" <wayne.bellamy at>
SAS Scenario:
1) A write command is issued to a SAS target, any HDD target...
2) this target reconnects and provides an SSP XFER_RDY frame for the
complete write data transfer length...
3) later, midway through this transfer of data frames the target
provides ACK and CREDIT_BLOCKED...
4) the initiator issues DONE(CREDIT TIMEOUT) since credit has not been
provided and CLOSEs the connection (target had issued DONE(NORMAL) after
the aforementioned XFER_RDY in 2)).

1) In this disconnected situation, write operation incomplete, which
device should reconnect to continue to complete this write operation?
(target or initiator?)
2) Can the target reconnect and issue a new XFER_RDY for the remainder
of the transfer or is it required that the initiator reconnect (or keep
trying to reconnect) to finish the transfer?
3) Somehow it seems incorrect for the initiator to continue to try to
reconnect to the target to finish the transfer. It seems incorrect to
put this management effort onto the initiator. In pSCSI the target
managed when it was ready to reconnect (to finish a data transfer) and
data phase/transfer control.


Grateful for all replies,

Wayne Bellamy=20
ISS - HDD Storage - Adv Tech Eng
Loc. CCA15 - 159A28
281-514-5196 fax 281-514-3200=20
email: wayne.bellamy

* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at

More information about the T10 mailing list