Re: [seul-edu] How big a server?

[Andrew Reid <andrew.reid@plug.cx>]

On Wed, Nov 14, 2001 at 12:20:13AM -0600, Les Richardson wrote:

> > Interesting comment -- "Sunray appliances (X Terminal
> > Wannabees)". They're not exactly X Terminals. There's a lot that's
> > done differently that makes the SunRay fairly different.
> 
> Perhaps true. But functionally from a software perspective they are.
> However there are issues....bandwidth consumption between Sunray and Sun
> server is horrific...each one _really_ needs dedicated 10Mbit/s to work.
> There's more.....<grin>

Functionality wise, yes. However, take a look under the hood (and as
you've mentioned -- have a look at traffic graphs on the switch :-),
they're quite different.

> > It seems to be the case when rolling out large quantities of SunRays
> > that you end up with more server power than you thought you
> > needed. This is generally because the analysis work at the school
> > didn't function correctly, giving the people at Sun the wrong idea.
> 
> Actually they Sun 450's don't have the horses to do it. (even though they
> could run 10,000 normal terminals...) Most services including
> authentication (NIS) and home directories have been moved onto separate
> Linux servers. Same thing with applications, primarily netscape and star
> office. They're going on Linux app servers.

Indeed. That's part of the SunRay architecture. The ability to run
applications on one machine, have another as the display server and
another doing authentication is a good thing. 

> > > example, then 50 users will need about 5GB of Ram. Typically one can stuff
> > > about 3-4 GB per server (even a Sun...4GB per processor). So perhaps build
> > > a couple of server to start.
> > 
> > ... but remember that not all your users are going to suck 100MB all
> > the time. If they're just running Nutscrape for example, you could
> > chop some of that figure off.
> 
> Netscape is a pig for ram. Also Flash _is_ a requirement in schools, since
> they _just gotta_ use it to see interesting sites. Flash kills the
> servers. Netscape alone perhaps would be fine, but add flash and demands
> go through the roof. One errant Netscape can bring a 450 to it's knees.
> Not good.

Yes, Netscape is a memory pig :-) However, you *can* prevent users
from killing the server. I borrowed a SunBlade 100 from Sun a couple
of weeks ago, and had a play with the process accounting stuff.

Without it, a normal user can completely kill the server, just by
using perl. Consider:

	perl -e "while (1) { fork() }"

We had to physically reboot the machine to regain control.

> > Bear in mind though, the SCSI
> > controller is going to have a limit to the amount of data that it can
> > move per-second. So, if you put 4 80MB/second drives on the one
> > interface, the maximum (theoretical) amount of data per-second that
> > any one drive could move (whilst other drives are also transferring
> > data at their maximum speed), is 20MB/second.
> 
> The new 160MB/sec interfaces can certainly push a lot of drives before
> you're scsi bus bound. Real world performance for a drive probably doesn't
> exceed 5-10MB given a lot of seeks, etc. Also, we don't put that many in
> for most servers. Just build more servers...

Definately. Those who think it's better to just stick more hard drives 
into the server(s) should be shot. It makes backup increasingly harder 
and you're putting all your eggs in the one basket.

> The Sun servers have 10 - 10k scsi drives but those boys have I/O to burn.
> In those boxes it is used to give more "virtual ram" to enable them to run
> the Sunrays. A poor engineering match in my view. (I don't really like the
> Sunray at all...they're pretty, but a real X terminal would be a much
> better solution IMHO.)

Hrm, well, no, I don't think I'd agree. The SunRay's are a pretty damn 
good solution. They've got some neat administration tools, as well as
the built-in smart card capability. The fact that they're running
Solaris is somewhat of a downside, but I can get over that :-)

> > Have you got an rsync-based system for keeping your windows boxes
> > up-to-date too? I've got that kind of thing happening under
> > Linux/FreeBSD, but not under Windows (using rsync).
> 
> Windows and "Up to Date" must be an oxymoron... No, we just ghost them and
> then lock them down using Deep Freeze. Very little required in the way of
> management, other than periodically updating the image, and reghosting. We
> try to get them as close to being a terminal as we can. 

Hrm, that's what we're currently doing. It's tedious and painful to
have to do that to an entire rooms though. I've had a look at PCRDist, 
which (whilst commercial), may be quite useful. Similar to Rsync it
seems. It's got a few holes, though. Perhaps we'll make our own solution.

   - andrew

-- 
Andrew J. Reid                    "Catapultam habeo. Nisi pecuniam omnem  
andrew.reid@plug.cx               mihi dabis, ad caput tuum saxum immane 
+61 401 946 813                   mittam"