On Mon, Dec 10, 2012 at 02:05:09AM -0500, Greg Smith wrote: > On 11/14/12 2:11 AM, Toby Corkindale wrote: > >So on the face of it, I think the Sandforce-based drives are probably a > >winner here, so I should look at the Intel 520s for evaluation, and > >whatever the enterprise equivalent are for production. > > As far as I know the 520 series drives fail the requirements > outlined at http://wiki.postgresql.org/wiki/Reliable_Writes and you > can expect occasional data corruption after a crash when using them. > As such, any performance results you get back are fake. You can't > trust the same results will come back from their drives that do > handle writes correctly. I'm not aware of any SSD with one of these > compressing Sandforce controller that's on the market right now that > does this correctly; they're all broken for database use. The quick > rule of thumb is that if the manufacturer doesn't brag about the > capacitors on the drive, it doesn't have any and isn't reliable for > PostgreSQL. > > The safe Intel SSD models state very clearly in the specifications > how they write data in case of a crash. The data sheet for the 320 > series drives for example says "To reduce potential data loss, the > Intel® SSD 320 Series also detects and protects from unexpected > system power loss by saving all cached data in the process of being > written before shutting down". The other model I've deployed and > know is safe are the 710 series models, which are the same basic > drive but with different quality flash and tuning for longevity. > See http://blog.2ndquadrant.com/intel_ssds_lifetime_and_the_32/ for > details. The 710 series drives are quite a bit more expensive than > Intel's other models. It looks like the newer Intel 330 SSD also lacks a capacitor. -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
