On Fri, Jun 27, 2008 at 7:00 AM, Matthew Wakeling <[EMAIL PROTECTED]> wrote: > On Thu, 26 Jun 2008, Merlin Moncure wrote: >> >> In addition there are many different types of flash (MLC/SLC) and the >> flash cells themselves can be organized in particular ways involving various >> trade-offs. > > Yeah, I wouldn't go for MLC, given it has a tenth the lifespan of SLC. > >> The main issue is lousy random write performance that basically makes them >> useless for any kind of OLTP operation. > > For the mentioned device, they claim a sequential read speed of 100MB/s, > sequential write speed of 80MB/s, random read speed of 80MB/s and random > write speed of 30MB/s. This is *much* better than figures quoted for many > other devices, but of course unless they publish the block size they used > for the random speed tests, the figures are completely useless.
right. not likely completely truthful. here's why: A 15k drive can deliver around 200 seeks/sec (under worst case conditions translating to 1-2mb/sec with 8k block size). 30mb/sec random performance would then be rough equivalent to around 40 15k drives configured in a raid 10. Of course, I'm assuming the block size :-). Unless there were some other mitigating factors (lifetime, etc), this would demonstrate that flash ssd would crush disks in any reasonable cost/performance metric. It's probably not so cut and dry, otherwise we'd be hearing more about them (pure speculation on my part). merlin -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
