On Fri, Apr 29, 2011 at 1:23 AM, Toby Corkindale <toby.corkindale@xxxxxxxxxxxxxxxxxxxx> wrote: > On 29/04/11 16:35, Greg Smith wrote: >> >> On 04/26/2011 10:30 AM, Toby Corkindale wrote: >>> >>> I see Intel is/was claiming their SLC SSDs had a *minimum* lifetime of >>> 2PB in writes for their 64GB disks; for your customer with a 50GB db >>> and 20GB/day of WAL, that would work out at a minimum lifetime of a >>> million days, or about 273 years! >>> The cheaper "consumer grade" MLC drives should still last minimum 5 >>> years at 20GB/day according to their literature. (And what I found was >>> fairly out of date) >>> That doesn't seem too bad to me - I don't think I've worked anywhere >>> that keeps their traditional spinning disks in service beyond 5 years >>> either. >> >> >> The comment I made there was that the 20GB/day system was a very small >> customer. One busy server, who are also the ones most likely to want >> SSD, I just watched recently chug through 16MB of WAL every 3 >> seconds=450GB/day. Now, you're right that those systems also aren't >> running with a tiny amount of flash, either. But the write volume scales >> along with the size, too. If you're heavily updating records in >> particular, the WAL volume can be huge relative to the drive space >> needed to store the result. > > For that sort of workload, it does sound like SSD isn't ideal. > Although if the Intel figure of 2PB is to be believed, it'd still take >200 > years to wear the drives out (assuming you'll need at least ten 64 GB disks > just to store the DB on). > (Reference: http://download.intel.com/design/flash/nand/extreme/319984.pdf ) I think you misunderstood. He's not storing 480GB on the drives, that's how much WAL is moving across it. It could easily be a single 80GB SSD drive or something like that. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
