Robert Haas wrote:
> I'm kind of surprised that there are disk I/O subsystems that are so
> bad that a single thread doing non-stop I/O can take down the whole
> server. Is that normal?
No.
> Does it happen on non-Windows operating
> systems?
Yes. My 3ware 8500-8 on a Debian Sarge box was so awful that launching a
terminal would go from a 1/4 second operation to a 5 minute operation
under heavy write load by one writer. I landed up having to modify the
driver to partially mitigate the issue, but a single user on the
terminal server performing any sort of heavy writing would still
absolutely nuke performance.
I landed up having dramatically better results by disabling the
controller's RAID features, instead exposing each disk to the OS
separately and using Linux's software RAID.
> What kind of hardware should I not buy to make sure this
> doesn't happen to me?
3ware's older cards. Apparently their new ones are a lot better, but I
haven't verified this personally.
Anything in RAID-5 without a BBU.
Anything at all without a BBU, preferably.
--
Craig Ringer