> >this is true, but extremely conservative/paranoid. it makes a lot > >of sense if you're handling banking transactions or if you really > >see a lot of abrupt power-offs (yank the battery). what are the chances > >of a drive failing to write dirty blocks when idle, halting? > > > The write cache in modern drives is multiple megabytes - 8 or 16MB is > not uncommon. The chances that you have data that is lost on a power > failure in the write cache is actually quite high... but we're not talking about power failures in the middle of peak activity. afaikt, drives also never dedicate their whole cache to writeback - they keep plenty available for reads, as well. it would also be rather surprising if the firmware was completely oblivious about limiting the age of writebacks; after all always delaying writes until you run out of cache capacity is _not_ a winning strategy (even ignoring safety issues.) during a normal shutdown, can you think of some reason the drive would have LOTS of outstanding writes? that's the real point. depending on kernel version, linux should be doing a cache-flush command and standby, then eventually calling bios poweroff. it's very possible that this is going wrong (rumors of disks that claim to implement, but ignore cache-flush, or perhaps ones that stupidly don't flush on standby, or even bios poweroff that happens so fast that the disks isn't done flushing...) but turning off all writeback is overkill (especially when there's some other obvious sign of distress...) - : send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
