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

One can also use methods that are provided by the disks to do media error testing. SCSI has a WRITE LONG command that can be used to corrupt a block by writing data with invalid ECC. SATA and NVMe also have similar commands.

For the most common case (SATA) you can use hdparm with --make-bad-sector to employ that command, you can use sg_write_long for SCSI and for NVMe you can use the nvme-cli with the write-uncor option.

The big advantage that these commands have over other injection methods is that they also behave just like a drive does, with full latency impacts and also the recovery upon a write to that sector by reallocation. This includes also error counters going up in the drive.

The disadvantage is that if you do this too much for the same drive its error counters will go up and SMART may flag the disk as bad or you may exhaust its reallocation tables. So do use it for manual testing but if you are running it on automated testing don't do it too often.