virtual memory swap size

[Gregory Mingus]

Thought I'd toss my opinion out...

I currently run a system with 45 users. It's a PIII-550 w/ 384MB RAM, RH 6.2
w/ a stripped kernel. This machine runs apache/PHP/MySQL, Qmail, POP3,
IMAP4, NetSaint, Snort, BIND, quite a few Cron jobs, and even Seti@home (at
nice -20). It runs great! I've already had over 6 months uptime on this box,
and only rebooted once so I could go from 128 to 384 megs. Even with the 128
megs, it ran fine. free -m shows a meg or two swap in use, but I think
that's normal after extended uptime and by no means is there any thrashing.

Only 140 megs are in use, 240 is disk cache. Absolutely great performance.
50,000+ hits/month from internal users without a wimper.

I'm not saying don't add more RAM, I'm just saying you probably won't need
it.

As for swap size, I chose 2x the RAM when I installed the system with 128
megs(256MB). As for the room on the drive swap takes? I don't think I'm
going to notice it missing from a 20gig drive. Especially since I don't do
mp3's or pr0n (At least not at work :)

That's my 2 bits.

-Greg-



-----Original Message-----
From: plug-discuss-admin@lists.PLUG.phoenix.az.us
[mailto:plug-discuss-admin@lists.PLUG.phoenix.az.us]On Behalf Of Craig
White
Sent: Monday, May 14, 2001 9:27 PM
To: plug-discuss@lists.PLUG.phoenix.az.us
Subject: RE: virtual memory swap size


> -----Original Message-----
> From: plug-discuss-admin@lists.plug.phoenix.az.us
> [mailto:plug-discuss-admin@lists.plug.phoenix.az.us]On Behalf Of KevinO
> Sent: Monday, May 14, 2001 7:51 PM
> To: plug-discuss@lists.plug.phoenix.az.us
> Subject: Re: virtual memory swap size
>
>
> Craig White wrote:
>
> > I am amazed at the diversity of opinion here. It would seem
> that 2X is safe
> > but not necessarily going to be the fastest setting. My
> interest is because
> > I am going to set up what is likely to be my first server that
> will actually
> > be serving a fair amount of web pages and it would seem that I
> have to make
> > allowances for this thing to keep running - even if it goes
> slow by way of
> > VM. It has 128M RAM but I think that it's necessary to upgrade
> it to 512K -
> > RAM's cheap anyway. I don't mind giving away 1 gigabyte of
> memory over to VM
> > if it's gonna help to keep this thing alive.
> >
>
> The more ram the merrier. If you are thinking of running X and a web
> server at
> the same time (gasp), upgrade to more ram.
>
> Having a swap file, of any size, will not slow down your machine. Not
> having one,
> and running out of memory will mean a crash.
>
> So go for the 512 MB, and add a swap file for those 'just in case' times
> ...
>
> You can always start with a 150 to 250 MB swap file and then watch the
> box to
> make sure you don't need more. If you do run out of ram and start to
> swap, things
> a r e  g o i n g  t o  s l o o o w  d o w n . . . . . but at least it
> won't crash.
>
> Expect the amount of 'free ram' displayed to dwindle down towards zero
> at times.
> It doesn't necessarily mean that you don't have any ram available, the
> kernel just
> hates to see any extra go to waste. It will be used for buffers/disk
> cache and be
> returned to use as soon as the box has something better to do with it...
>
> Yes, this means more ram than you 'need' can speed things up since you
> don't need
> to load something from disk if it is already in ram.
>
> 512MB is a pretty large chunk of ram unless you are running a LARGE
> load.
>
> YMMV
>
-----
I'm gathering that running Apache/PHP4/MySQL for imp is a resource pig. I
play with it at home but I only have one user (me). Here, we may have 10-20
users online at any time.

Thanks,

Craig

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