G S wrote:
Howdy, I have a Linux (2.6) using Emulex and QLogic FC HBA's to a disk array product, with a single LUN presented, say LUN 1. The dsf is created for LUN 1 and i can send SCSI commands to LUN 1. And i'm using "sg". If i delete LUN 1 from disk array. Reboot the disk array. Array boots up only with LUN 0. I have recreated LUN 1 on the target storage array. But any attempt to send SCSI command to LUN 1 fails because LUN 1 has been marked offline by SCSI mid layer. Why? Is it because RSCN seen by HBA driver is passed up to SCSI mid layer to trigger re-scan? And re-scan no longer finds LUN 1, so LUN 1 kernel structures are torned down, and LUN 1 marked offline by SCSI mid layer?
If I understand your sequence correctly, rebooting the disk array would cause a RSCN to the HBA, and that would cause it to delete LUN 0 and 1. When the disk array comes up and logs into the fabric again, another RSCN goes to the HBA and it sees the target (array) and presents it to the transport layer and SCSI. It scans LUN0 (does REPORT LUNS) and it reports no other LUNs. No LUN 1 at this point. Then you add LUN 1 on the array. There's no event caused by that as far as I know. I'm not a complete expert on this and it depends on your array, I think. It may cause an check condition on the next I/O that goes to LUN0, but that may never happen. So nothing happens on the server. It doesn't cause an RSCN because the array didn't re-login to the fabric (that would be disruptive for other initiators).
Doing following to add back LUN 1 will bring it back for access, # echo "scsi add-single-device <H> <B> <T> <L>" > /proc/scsi/scsi Above "echo" seems to cause a blind re-scan by sending SCSI INQUIRY to LUN 1 on the h/b/t/l hardware path. That SCSI INQUIRY succeeds. And that success seems to cause LUN 1 to be marked online again.
OK. I think you can also echo 1 to /sys/class/scsi_host/hostX/scan I hope that helps and someone will correct me if any of this is wrong. Joe -- To unsubscribe from this list: 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
