Re: swap

[Ron Johnson <ron.l.johnson@cox.net>]

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On 05/10/07 18:10, Douglas Allan Tutty wrote:
[snip]
> 
> I guess I wasn't clear.  I wasn't suggesting to use memory as swap.  I
> was wondering about ways to get swap that was faster than a disk array
> and wondering if it could be farmed out to other boxes and present
> something which could be swapped to faster (ideally approaching memory
> speed).  For example, if your box _was_ maxxed out on memory but the
> program still wanted to pull in _all_ the data to memory at once and it
> wouldn't fit, so it swaps; then what if you had something like a SAN
> that could present a block device that functioned as fast as memory,
> this block device actually being run by (an)other processor(s) on the
> same machine?

*If* you had such a device, it would be *great*.  But you don't.

It's impossible, if for no other reasons than that the rotational
speeds of disks (3 microseconds) are many orders of magnitude slower
than the access speed of RAM (80 nanoseconds, many many years ago).

And if you say "make a SSD", then I say that it's still slower than
RAM because disk channel bandwidth is still *much* slower than
memory bandwidth.  Better to spend that money on extra RAM.

- --
Ron Johnson, Jr.
Jefferson LA  USA

Give a man a fish, and he eats for a day.
Hit him with a fish, and he goes away for good!

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