[R] Help with large datasets

[Trent Piepho]

On Tue, 20 Mar 2001, Paul Gilbert wrote:
> In Unix I think this is a limit imposed by swap space (and the amount of other
> activity on the machine) and is not restricted by physical memory. If you just added
> a lot of ram to your machine then it is possible your swap space is smaller than your
> physical memory (which doesn't make sense and you probably should increase swap).

Some older unix variants are like this.  The idea is that disk storage is the
real "memory", and the core (RAM) is just a "cache" for the disk memory. 
Everything is stored on disk, with a few megabytes cached in memory, and a few
kilobytes in the sram cache memory.  If you have 100MB of disk memory, and 4MB
of RAM memory, you have 100MB total storage.  If you had 100MB disk, 500MB
RAM, you would still only have 100MB total storage.

Linux doesn't do this.  If you have 32MB of disk swap and 16MB of memory, your
total storage would be 48MB.  I have 512MB of ram on this machine, but only
128MB of swap.  Any program without a memory leak that uses more than 128MB of
swap would be trashing so badly as to be pointless.

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