Re: [Ltsp-discuss] RAM requirements

[Scott B. <sba...@le...>]

On Wed, Dec 16, 2009 at 10:44:45AM -0500, Stéphane Graber wrote:
> Scott Balneaves wrote:
> > On Wed, Dec 16, 2009 at 02:33:39PM +0000, Evan Ingram wrote:
> >> hi
> >>
> >> i've seen various numbers quoted for ram requirements on an ltsp server;
> >> "ranging from 256Mb + 32Mb per client to 1024Mb + 64Mb per client."
> >>
> >> what are peoples findings in the real world? i need to spec up a server
> >> for a school implementation of about 64 workstations, so needs to
> >> perform usual web/office/multimedia tasks.
> > 
> > What we officially recommend in the upstream documentation is:
> > 
> > 256 + (192 * users) MB
> > 
> > So, for 64 users, you'd be wanting a s server with at least:
> > 
> > 256 + (192 * 64) ~= 12 gigs of ram.
> 
> I guess we'll need to change that a bit in the doc then ;)
> I had up to 70 users on a single QuadCore server with 8GB of RAM and 
> there still was a Gig or so of free memory.

Well, sure, there's always special cases.  I mean, if you have people using
nothing but mutt and vi in an xterm, one server may potentially serve well over
150 users. :)

> I guess the above calculation is correct if your run everything 
> (including firefox) on the application server and have your users do 
> very different activities.

IIRC, we came up with that figure by having evolution, firefox, and openoffice
opened simultaneously.  I've always maintained LTSP server sizing's more of a
black art than anything.  Our usual response in the channel to people who ask
"How much ram?" is "what do you want to run?"

> On some of the very big deployments I have here, a user usually uses 
> less than 80MB of RAM on a non-loaded server (35 users when designed for 
> 100 or so).
> 
> So, at least for Ubuntu Karmic, I'd say it's more like:
> 512MB (to take the recommendation from Ubuntu) + (80  * users) MB

I've got one server with about 40 people.  Typical usage for these people would
be 2-3 firefox windows, thunderbird, and openoffice opened simultaneously.
I've got 8 gigs of ram in it, and every once it a while it touches swap.  But
not often.

> And if firefox isn't local, I'd probably make that 80 a 120 as it's 
> eating a lot of memory.

Right, localapps will change your memory requirements drastically.

> > Practically speaking, from a load averaging perspective, you'd do better to buy
> > 2 servers, and split the load between them.  A nice quad core with 8 gigs of
> > ram isn't that expensive, and that will comfortably handle 32 users.
> 
> Splitting load across servers is always a good idea, that will also let 
> you afford having one server done for a while in case of emergency.

Yep!

Scott

-- 
Scott L. Balneaves | The human race has one really effective weapon,
Systems Department | and that is laughter.
Legal Aid Manitoba |     -- Mark Twain