SAS Transport Layer Retries Teleconference Question

Jim Jones (Engineering) Jim.Jones at quantum.com
Tue Jan 28 16:25:06 PST 2003


* From the T10 Reflector (t10 at t10.org), posted by:
* "Jim Jones (Engineering)" <Jim.Jones at Quantum.com>
*
Paul Entzel and I worked with Dave Peterson on forming the question to ask
backup application providers.  Here it is:

The T10 committee is currently working on a standard that does not include
transport layer error recovery.  Errors detected at the transport layer
would result in commands returned with aborted command status.  It is
possible that this aborted status may be returned following the successful
completion of a command.  Some concern has been expressed as to whether
backup applications can deal with this.

The T10 committee is requesting feedback from backup application providers
indicating the extent of error recovery in current backup applications
(i.e., are the READ POSITION and LOCATE commands used for error detection
and recovery purposes).

We would like backup application providers to respond to the following
question:

If you receive aborted status for a write, read, or space command that may
or may not have completed successfully, will the backup application recover
at the application layer?  

The necessary recovery may include detecting whether the command completed
successfully (e.g., using READ POSITION), issuing a reposition command
(e.g., using LOCATE), and reissuing the failing command.

For example, if a write command returns aborted command status, the backup
application needs to determine the current location, reposition to the
location prior to the write command and reissue the write command.

Using another example, if a space command returns aborted command status,
the backup application needs to determine the current location, and perform
the appropriate operation to complete the space command.

__________________________
Jim Jones
4001 Discovery Dr., Suite 2100
Boulder, CO 80303
Jim.Jones at quantum.com
720-406-5611
 

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