ZFS vfs.zfs.cache_flush_disable and ZIL reliability

[Marcus Reid]

On Thu, Mar 17, 2011 at 12:45:58AM -0700, Jeremy Chadwick wrote:
> General question to users and/or developers:
> 
> Can someone please explain to me why people are so horribly focused (I
> would go as far to say OCD) on this topic?
> 
> Won't there *always* be some degree of potential loss of data in the
> above two circumstances?  Shouldn't the concern be less about "how much
> data just got lost" and more about "is the filesystem actually usable
> and clean/correct?"  (ZFS implements the latter two assuming you're
> using mirror or raidz).

I'm going to venture that it's so important because it's the one big
most likely thing to go wrong if you're not using the right hardware
or aren't configured right.  Don't want to be that guy with the bad
pool reaching for the backup tapes.

Was also just curious to lay my eyes on the line that flushes the cache
and was having a hard time finding it :/

> Sorry for the rant, I just keep seeing this topic come up over and over
> and over and over and over and it blows my mind.

I did search around a bit and couldn't find an old thread.  The topic
of disk caches and all the stuff around it has come up a lot over the
years, but not quite in this context.

Marcus