Re: Reliability with RAID 10 SSD and Streaming Replication

On 5/20/13 6:32 PM, Merlin Moncure wrote:

> When it comes to databases, particularly in the open source postgres
> world, hard drives are completely obsolete.  SSD are a couple of
> orders of magnitude faster and this (while still slow in computer
> terms) is fast enough to put storage into the modern area by anyone
> who is smart enough to connect a sata cable.

You're skirting the edge of vendor Kool-Aid here.  I'm working on a very
detailed benchmark vs. real world piece centered on Intel's 710 models,
one of the few reliable drives on the market.  (Yes, I have a DC S3700
too, just not as much data yet)  While in theory these drives will hit
two orders of magnitude speed improvement, and I have benchmarks where
that's the case, in practice I've seen them deliver less than 5X better
too.  You get one guess which I'd consider more likely to happen on a
difficult database server workload.

The only really huge gain to be had using SSD is commit rate at a low
client count.  There you can easily do 5,000/second instead of a
spinning disk that is closer to 100, for less than what the
battery-backed RAID card along costs to speed up mechanical drives.  My
test server's 100GB DC S3700 was $250.  That's still not two orders of
magnitude faster though.

--
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com