On Fri, Oct 9, 2009 at 1:28 PM, Ray Van Dolson <rayvd at bludgeon.org> wrote: > Really hard to say what's going on. Does your DB need optimization? > Do the applications hitting it? Maybe some indexing? Maybe some more > RAM on the machine would help? What exactly is the workload like -- > especially during the time when you're peaked out? Yes, these are all things we are just starting to look at - so no clear answers yet > Is the system swapping? If so, you either need more memory or need to > track down a memory leak.... 'free' and 'sar' can both help you see > what swap usage is like. That's one thing it does not seem to be doing, fortunatley. > Writes are always slower on any parity based RAID setup, so I imagine > you'd get superior performance on RAID10, especially if you're write > heavy. We are generally read heavy but at certain times of day including 6 to 9am we have huge batches of writes. > But to begin with, it'd be interesting to know exactly what this server > is doing. Does it makes sense that the disks are being brought to > their knees with the given workload? Oh yes! We are a financial services provider and the Db contains all of the worlds stock prices for about the last 10 years :-) And every day new batches of prices come in (at different times depending on markets). This system is just a PostgreSQL DB. Nothing else. > Is the disk array you bought an N-series? (N3300, N3600)? If so, those > are NetApps and should be quite fast thanks to heavy write caching. > Even then, you'll be limited by spindles it sounds like... No, the array is IBM brand. EXP3000 (I've since looked it up) -- “Don't eat anything you've ever seen advertised on TV” - Michael Pollan, author of "In Defense of Food"