WRITE ATTRIBUTE and the write-through cache bit

Kevin D Butt kdbutt at us.ibm.com
Tue Sep 1 12:03:27 PDT 2015


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1509010_f.htm">HTML-formatted message</a>

SPC-5 states in the WRITE ATTRIBUTE command:
The write-through cache (WTC) bit set to one specifies the attributes in 
the parameter list shall be synchronized
with the medium auxiliary memory during the processing of the WRITE 
ATTRIBUTE command and GOOD
status shall not be returned until the attributes have been synchronized 
with the medium auxiliary memory.
The WTC bit is set to zero specifies no requirement related to the 
attributes in the parameter list being
synchronized with the medium auxiliary memory during the processing of the 
WRITE ATTRIBUTE command.
The PARAMETER LIST LENGTH field specifies the length in bytes of the 
parameter list contained in the Data-Out
Buffer. A parameter list length of zero specifies that no parameter list 
is present; this shall not be considered
an error. If the parameter list length results in the truncation of an 
attribute, the WRITE ATTRIBUTE command
shall be terminated with CHECK CONDITION status, with the sense key set to 
ILLEGAL REQUEST, and the
additional sense code set to PARAMETER LIST LENGTH ERROR.
If the parameter list length is zero, the expectation is that this command 
is a no-op and nothing happens. However, by a strict reading of the text, 
there is no exclusion of the requirement to synchronize the cache if the 
WTC=1b.  I believe this is an oversight and the intended behavior when 
WTC=1b and parameter list length=zero is to return GOOD status with no 
action.
Does anybody disagree?
Thanks,
Kevin D. Butt
SCSI Architect, Tape Firmware, CAMSS
T10 Standards
MS 6TYA, 9000 S. Rita Rd., Tucson, AZ 85744
Tel: 520-799-5280
Fax: 520-799-2723 (T/L:321)
Email address: kdbutt at us.ibm.com
http://www-03.ibm.com/servers/storage/ 



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