On Fri, Oct 9, 2009 at 1:28 PM, Ray Van Dolson rayvd@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)