How can I simulate a failed disk during testing?

Question

In a Linux VM (Vmware workstation or similar), how can I simulate a failure on a previously working disc?

I have a situation happening in production where a disc fai

Answer 1

You may use scsi_debug kernel module to simulate a RAM disk and it supports all the SCSI errors with opts and every_nth options.

Please check this http://sg.danny.cz/sg/sdebug26.html

Example on medium error on sector 4656:

[fge@Gris-Laptop ~]$ sudo modprobe scsi_debug opts=2 every_nth=1
[fge@Gris-Laptop ~]$ sudo dd if=/dev/sdb of=/dev/null
dd: error reading ‘/dev/sdb’: Input/output error
4656+0 records in
4656+0 records out
2383872 bytes (2.4 MB) copied, 0.021299 s, 112 MB/s
[fge@Gris-Laptop ~]$ dmesg|tail
[11201.454332] blk_update_request: critical medium error, dev sdb, sector 4656
[11201.456292] sd 5:0:0:0: [sdb] FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
[11201.456299] sd 5:0:0:0: [sdb] Sense Key : Medium Error [current] 
[11201.456303] sd 5:0:0:0: [sdb] Add. Sense: Unrecovered read error
[11201.456308] sd 5:0:0:0: [sdb] CDB: Read(10) 28 00 00 00 12 30 00 00 08 00
[11201.456312] blk_update_request: critical medium error, dev sdb, sector 4656

You could alter the opts and every_nth options in runtime via sysfs:

echo 2 | sudo tee /sys/bus/pseudo/drivers/scsi_debug/opts
echo 1 | sudo tee /sys/bus/pseudo/drivers/scsi_debug/opts