Re: how far unclean shutdowns can corrupt MyISAM tables ?

[Ingo Strüwing]

Normally, during system shutdown, all processes get a SIGTERM before they get a SIGKILL. SIGTERM will normally trigger a clean shutdown of mysqld. You can check this in the error log. It is unlikely, but not impossible, that the MySQL shutdown is interupted by the SIGKILL if it follows too fast after the SIGTERM.

But even without a MySQL shutdown I would not expect table corruption unless you use --delay-key-write.

Another chance for corruption is by heavy concurrency. See the thread "Often corrupt table indexes" in this forum. The respective bug could not yet be found.

Another chance for corruption is having characters with codes less than 'blank' in varchar columns (e.g. carriage return, tab, or newline). Recently I fixed the third bug regarding this. It will probably be in 4.1.15. See Bug #12565 (Bug #6151 and Bug #9188 have already been fixed in 4.1.7 and 4.1.12 respectively).