server has stopped responding 2x the past week. can't authenticate locally, web servers are not responding, etc. reboot seems to resolve the issue temporarily, but it looks like a disk or controller failure. some output from dmesg and sfdisk below.

dmesg errors:
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
Vendor: SEAGATE Model: ST914602SSUN146G Rev: 0400
Type: Direct-Access ANSI SCSI revision: 05
sdb: Spinning up disk................................................................................................ .not responding..
.
sdb : READ CAPACITY failed.
sdb : status=1, message=00, host=0, driver=08
Current sd: sense key Not Ready
Additional sense: Logical unit not ready, cause not reportable
sdb: asking for cache data failed
sdb: assuming drive cache: write through
sdb: Spinning up disk................................................................................................ .not responding..
.
sdb : READ CAPACITY failed.
sdb : status=1, message=00, host=0, driver=08
Current sd: sense key Not Ready
Additional sense: Logical unit not ready, cause not reportable
sdb: asking for cache data failed
sdb: assuming drive cache: write through
sdb:<6>Device sdb not ready.
end_request: I/O error, dev sdb, sector 0
Buffer I/O error on device sdb, logical block 0
Device sdb not ready.
end_request: I/O error, dev sdb, sector 0
Buffer I/O error on device sdb, logical block 0
Device sdb not ready.
end_request: I/O error, dev sdb, sector 0
Buffer I/O error on device sdb, logical block 0
Device sdb not ready.

# sfdisk -V /dev/sdb
read: Input/output error

sfdisk: read error on /dev/sdb - cannot read sector 0
/dev/sdb: unrecognized partition

sfdisk: no partition table present.

Hi,

Welcome to LQ!

We will aid you when you help yourself to a solution. Provide us with what you have attempted and then maybe someone will be able to assist. Posting the logs is one thing but what has been done and what is the result from the attempts to correct the problem? Check the cables? Power supply? Did the manufacture diagnostics on the disk(s)? Do a search here on LQ or Google for trouble-shooting techniques? Some effort on your part is required, not just throwing out a problem and expect a solution. Especially since the information provided is not complete.

'How to Ask Questions the Smart Way' would be one link you should look at to help us to help you in the future.

Just a few more links to aid you;

Linux Documentation Project
Rute Tutorial & Exposition
Linux Command Guide
Utimate Linux Newbie Guide
LinuxSelfHelp
Getting Started with Linux
Bash Reference Manual
Advanced Bash-Scripting Guide
Linux Home Networking


The above links and others can be found at 'Slackware-Links'. More than just Slackware® links!

I had something similar on an MSI notebook (dualbooting with XP).

During Slackware startup, similar errormessages popped up. The system ran normally, however. In XP no messages were displayed and also no warnings.

Then, on a bad day, the machine refused to start. No XP and no Slackware. The disk was tested with the Hitachi Drive fitness test: http://www.hitachigst.com/support/downloads/ and found to be OK. Still, no actions were possible.

The laptop was still under warranty so I returned it to be fixed. It took the dealer 6 weeks to find out that the drive was OK, but the controller on the main board was gone. I was allowed o get a new laptop from their assortment. Now we have a Toshiba. Working fine.

So, if Linux reports a system error with your drives, do not wave it away. ACT NOW. Linux warnings come in an early stage. I would take no risks. Get the data off while you still can and install a new disk.
Leave this disk in as extra storage; you never know....