An old problem, very annoying. >From time to time, an scsi disk just disappears from the bus, without any [error] messages whatsoever. The only relevant stuff in dmesg is logging from md (softraid) layer, about "error updating superblock" and later "giving up and removing the disk from the array" - not even error number. When I try to access such a disk (/dev/sdX device), I got "No such device or address" error back. It's still listed in /sys/block and /proc/scsi/scsi, but any access to the device gives this error. But the disk is here, I know it is. Deleting it from kernel: echo y > /sys/block/sdX/device/delete and adding it back: echo scsi add-single-device x y z > /proc/scsi/scsi works just fine, linux finds "new" scsi device and it happily works again. This happens on alot of different machines, with different disk drives (ok, most of them are from Seagate, but not all). I can't say for sure that it happens on different scsi controllers - at least majority of them are adaptecs, using aic7xxx or aix79xx driver. I suspected the disks are too hot - nope, according to smartctrl, the themp is far from bad (typically about 25..35 Celsius, and the themperature is not changing much). Bad cables, bad power supply, bad anything else? Not sure either, at least I can't guess more: the machines are really different, some has good, under-loaded power supplies (and server chassis/motherboards/allthestuff) some has less good ones - makes no difference. And the thing is - having in mind really sporadic disappearing, not depending on current load, time of day (eg, during nights, there's no one on site so no one to touch cables etc), ... Well, I just can't think of any reason, at all. But one thing bothers me most: there's NO LOGGING from scsi layer. None, zero, not at all. Has anyone else seen something similar? Any pointers on how to debug the issue? Thanks. /mjt - 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
