Re: Slow Query / Check Point Segments

Greg Smith wrote:
> My guess is that there's something wrong with your config such that
> writes followed by fsync are taking longer than they should.  When I
> see "sync=0.640 s" into a SAN where that sync operation should be near
> instant, I'd be looking for issues in the ZFS intent log setup, how
> much data you've setup ZFS to write cache, and the write cache policy
> on the SAN hardware.  There's something weird going on here, that sync
> should be near instant on your hardware with such a small write volume.
>
> Unfortunately, you may have to take the server down to find out
> exactly what's going on, which doesn't sound practical for your
> environment.  (And people wonder why I have near religious zeal about
> testing disk hardware before systems go into production)


there's a further complication.   this system is deep in southeast asia
on a rather slow and saturated network connection such that trying to
figure out stuff about it is challenging at best.   I know the database
has a lot of write volume overall, and its only one of several databases
running in different zones on the server.  I know nothing about the SAN,
I suspect its a EMC Symmetrix of some sort.  Probably a generation or
two behind latest.   The operations people are used to running large
oracle databases.