Hi, I have question(s) regarding the fastfail operation of the SCSI stack. Performing multipath-tests with an IBM ESS I encountered problems. During certain operations on an ESS (quiesce/resume and such) requests on all paths fail temporarily with an data underrun (resid is set in the FCP-response). In another situation abort sequences happen (see FC-FS). In both cases it is not a path failure but the device (ESS) reports error conditions temporarily (some seconds). Now on error on the first path the multipath layer initiates failover to other available path(s) where requests will immediately fail. Using linux-2.4 and LVM such problems did not occure. There were enough retries (5 for each path) to handle such situations. Now if the FASTFAIL flag is set the SCSI stack prevents retries for failed SCSI commands. Problem is that the multipath layer cannot distinguish between path and device failures (and won't do any retries for the failed request on the same path anyway). How can an lld force the SCSI stack to retry a failed scsi-command (without using DID_REQUEUE or DID_IMM_RETRY, which both do not change the retry counter). What about a DID_FORCE_RETRY ? Or is there any outlook when there will be a better interface between the SCSI stack and the multipath layer to properly handle retries. Regards, Andreas - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
