My local kernel guru recognized this problem as a duplicate of the LSI8408E bus lockup problem. The controller gets flooded with work, and just climbs under a rock to hide. In the 8408E case, it froze the PCI-e bus :-) #!/bin/csh # # set the max request queue down from 128. any more than 32 # quickly slows down from 810MB/Sec to 11MB/Sec. # setenv X 32 # foreach i ( /sys/block/sd{g,h,i,j,k,l,m,n}/queue/nr_requests) echo $X > $i end Lots of time was spent in the congestion queue, like 99% of the time. Berkley This e-mail and any documents accompanying it may contain legally privileged and/or confidential information belonging to Exegy, Inc. Such information may be protected from disclosure by law. The information is intended for use by only the addressee. If you are not the intended recipient, you are hereby notified that any disclosure or use of the information is strictly prohibited. If you have received this e-mail in error, please immediately contact the sender by e-mail or phone regarding instructions for return or destruction and do not use or disclose the content to others. - 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