On Mon, Mar 2, 2009 at 12:37 PM, Warren Young <warren at etr-usa.com> wrote: > Dnk wrote: >> Is there any real advantage to using 64 bit when I am right at the 4gb >> ram threshhold? > > Yes, unless you're not turning on swap. Once you add swap to a system > with 4 GB of RAM, you need either PAE or 64-bit to actually use the > swap. Since 64-bit CPUs became cheap last year, there's no longer a > good reason to use PAE on a new system, so that means 64-bit. > > You can make much the same argument farther down the line....even with 2 > GB RAM and 2 GB swap, 64-bit might be the right configuration choice. > >> The machine will just be a backup machie (rsync). > > I doubt you'll actually use all that RAM, 64-bit or not. > > An rsync-only box should be completely I/O bound. If it were a choice > between more RAM and either another disk spindle or a hardware RAID > card, I'd choose the better disk setup, here. I assume you will have a > gigabit Ethernet link...the trick then is to saturate it, which you > can't do with a single disk, no matter how much RAM you've got, or how > much 64-bitness you throw at it. Fail to saturate the network link, and > you're slowing your backups. > > If the rsync box is on the other side of a slow network link, I'd still > go for a better disk setup over more RAM. In that particular case, I'd > be looking at things like hot spares, because it means you're probably > not always near the server to swap disks when they fail. You can definitely use the 2GB+ on an I/O bound box for disk caching! A lot of people underestimate the performance benefit of page cached backed I/O when building out storage boxes. -Ross