Re: SCSI target and IO-throttling

[Douglas Gilbert <dougg@torque.net>]

Vladislav Bolkhovitin wrote:
> Steve Byan wrote:

<snip>

> BTW, do you have any statistic how many modern SCSI disks support those
> features (ORDERED, ACA, UA_INTLCK_CTL, etc)? Few years ago none of
> available for us SCSI hardware, including tape libraries, supported ACA.
> It was not very modern for that time, though

Vlad,
Here is part of the control mode page from a
recent SCSI disk (Cheetah 15k.4) :

# sdparm -p co /dev/sdb -ll
    /dev/sdb: SEAGATE   ST336754SS        0003
    Direct access device specific parameters: WP=0  DPOFUA=1
Control mode page [PS=1]:
  TST         0  [cha: n, def:  0, sav:  0]  Task set type
        0: lu maintains one task set for all I_T nexuses
        1: lu maintains separate task sets for each I_T nexus
  TMF_ONLY    0  [cha: n, def:  0, sav:  0]  Task management functions only
  D_SENSE     0  [cha: n, def:  0, sav:  0]  Descriptor format sense data
  GLTSD       0  [cha: y, def:  1, sav:  0]  Global logging target save disable
  RLEC        0  [cha: y, def:  0, sav:  0]  Report log exception condition
  QAM         0  [cha: y, def:  0, sav:  0]  Queue algorithm modifier
        0: restricted re-ordering; 1: unrestricted
  QERR        0  [cha: n, def:  0, sav:  0]  Queue error management
        0: only affected task gets CC; 1: affected tasks aborted
        3: affected tasks aborted on same I_T nexus
  RAC         0  [cha: n, def:  0, sav:  0]  Report a check
  UA_INTLCK   0  [cha: n, def:  0, sav:  0]  Unit attention interlocks control
        0: unit attention cleared with check condition status
        2: unit attention not cleared with check condition status
        3: as 2 plus ua on busy, task set full or reservation conflict
  SWP         0  [cha: n, def:  0, sav:  0]  Software write protect
  ATO         0  [cha: n, def:  0, sav:  0]  Application tag owner
  TAS         0  [cha: n, def:  0, sav:  0]  Task aborted status
        0: tasks aborted without response to app client
        1: any other I_T nexuses receive task aborted

So it doesn't support UA_INTLCK ("cha: n" implies the user
cannot change that value). QAM can be changed to allow
unrestricted re-ordering (of task with the SIMPLE task
attribute).

The NormACA bit in the standard INQUIRY response is 0 so
it doesn't support ACA either.

Doug Gilbert