[NMLUG] Linux rocks

[sbrowne at ix.netcom.com (Steve Browne)]

On Mon, 26 Mar 2007 21:37:14 -0600, you wrote:

>Just thought I'd share some stuff that happened today.
>
>I just finished moving a LAMP(php/perl) stack over from a Pentium 4 3.4GHz/1GB
>RAM machine to a Pentium D 3.4/2GB RAM server.  There was about 1.5GB of
>data in the MySQL database, and the client had a long running query that
>would aggregate much of it and display it on a page.  It would normally take
>about 20-30 seconds to run.
>
>After moving over the scripts and database, the client tested the script,
>and as expected, it ran only slightly faster than it did on the other
>machine.  Then the client wanted to run two instances of the script and see
>how the dual core system handled it.  He started one, but before he could
>start the second, the first one was complete.  He was pretty concerned,
>thinking that something much have been broken by the move, and that a cached
>copy was being served.  How could a 30 second query be served in less than a
>second?
>
>A quick look at "free -m" showed that although the OS and LAMP stack was
>only taking 95MB of RAM, over 1.5GB was being used as cache.  The majority
>of the normal 30 second query time was spent reading the data off disk.
>After the first query, Linux cached all the database files in RAM, so the
>next time the queries didn't have to pull anything off disk.  That combined
>with MySQL's query cache made a big difference.  The client was pretty
>impressed.
>
>The moral?
>Linux's aggressive file system caching is a good thing (usually).
>Linux doesn't let unused RAM sit around doing nothing, and sometimes it
>shows in a big way.  So, if you can afford it, go for more RAM.

If you use a multipurpose system, that presents some problems. If you
have a legacy WinME shared installation, it won't run in more than
1.5Gb. RAM. If you have a shared XP installation, it won't run in more
than 4Gb. RAM. For a while Hiren's BootCD (FreeDOS) balked at more
than 2Gb. RAM, but the latest release (v8.9) has fixed that.

Moral: dump Windows, though DOS can still be handy.

Steve
Stephen B. Browne
sbrowne at ix.netcom.com
"Ubi bene, ibi patria."