Re: Testing Sandforce SSD

Matthew Wakeling wrote:
> Does your latency graph really have milliseconds as the y axis? If so,
> this device is really slow - some requests have a latency of more than
> a second!

Have you tried that yourself?  If you generate one of those with
standard hard drives and a BBWC under Linux, I expect you'll discover
those latencies to be >5 seconds long.  I recently saw >100 *seconds*
running a large pgbench test due to latency flushing things to disk, on
a system with 72GB of RAM.  Takes a long time to flush >3GB of random
I/O out to disk when the kernel will happily cache that many writes
until checkpoint time.

--
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us