[R] Speed up R

[Mike Prager]

"Matthew Keller" <mckellercran at gmail.com> wrote:

> Robert,
... 
> As for Mike Prager's point about the type of hard drive being
> important, I'm not sure this is right (someone correct me if I'm
> misunderstanding). R stores and accesses objects through RAM - they
> aren't stored and accessed on the hard drive except when reading and
> writing. So hard drive type probably won't make much difference to
> speed in R.

In my experience, it makes a substantial difference if any
swapping to disk is going on. That will happen if, e.g., other
processes or Windows itself need RAM. Though R keeps the data in
RAM, under Windows, non-SCSI disk I/O puts a noticeable load on
the CPU. As SCSI controllers have CPUs of their own, they
offload much of that work from the system CPU.

I have compared dual-processor computers with equal RAM, one
with a SCSI subsystem and one with fast (7200 RPM) ATA disks and
slightly faster CPUs.  One was my work machine, one my home. The
difference was not subtle.  For another example, think of how
slow laptops seem when multitasking, compared to a good
workstation. It is usually the poor disk subsystem that's the
bottleneck, not the CPU.

Mike

-- 
Mike Prager, NOAA, Beaufort, NC
* Opinions expressed are personal and not represented otherwise.
* Any use of tradenames does not constitute a NOAA endorsement.