This bug has been copied from bug #694625 and has been proposed to be backported to 5.7 z-stream (EUS).
in kernel-2.6.18-274.11.1.el5 linux-2.6-scsi-reduce-error-recovery-time-by-reducing-use-of-turs.patch
Cannot reproduce this problem on RHEL 5.7 GA kernel. scsi_debug downloaded from http://lacrosse.corp.redhat.com/~fge/scsi_debug/ ======= [root@intel-canoepass-02 ~]# modprobe scsi_debug dev_size_mb=100 opts=4 [root@intel-canoepass-02 ~]# date Wed Nov 23 05:03:52 EST 2011 [root@intel-canoepass-02 ~]# echo -1 > /sys/module/scsi_debug/parameters/every_nth [root@intel-canoepass-02 ~]# dd if=/dev/sdb of=/dev/null count=1 iflag=direct dd: reading `/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes (0 B) copied, 120.01 seconds, 0.0 kB/s [root@intel-canoepass-02 ~]# date Wed Nov 23 05:05:52 EST 2011 ======== Got same results on kernel-2.6.18-274.11.1.el5. Code reviewed, patch found in kernel-2.6.18-274.11.1.el5
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. http://rhn.redhat.com/errata/RHSA-2011-1479.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: In error recovery, most SCSI error recovery stages send a TUR (Test Unit Ready) command for every bad command when a driver error handler reports success. When several bad commands pointed to a same device, the device was probed multiple times. When the device was in a state where it did not respond to commands even after a recovery function returned success, the error handler had to wait for the commands to time out. This significantly impeded the recovery process. With this update, SCSI mid-layer error routines to send test commands have been fixed to respond once per device instead of once per bad command, thus reducing error recovery time considerably.