[CentOS] 32 or 64 bit (4 gb ram)
warren at etr-usa.com
Mon Mar 2 17:37:57 UTC 2009
> 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.
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