Craig James wrote:
Maybe this is a dumb question, but why do you care? If you have 1TB RAM and just a little more actual disk space, it seems like your database will always be cached in memory anyway. If you "eliminate the cach effect," won't the benchmark actually give you the wrong real-life results?
If you'd just spent what two FusionIO drives cost, you'd want to make damn sure they worked as expected too. Also, if you look carefully, there is more disk space than this on the server, just not on the SSDs. It's possible this setup could end up with most of RAM filled with data that's stored on the regular drives. In that case the random performance of the busy SSD would be critical. It would likely take a very bad set of disk layout choices for that to happen, but I could see heavy sequential scans of tables in a data warehouse pushing in that direction.
Isolating out the SSD performance without using the larger capacity of the regular drives on the server is an excellent idea here, it's just tricky to do.
-- Greg Smith 2ndQuadrant US greg@xxxxxxxxxxxxxxx Baltimore, MD PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us "PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
