Great stuff Tim, thanks for that.
Virtualisation is very much on my mind (and that of many others I expect), certainly for web interfaces.
Currently all I have to work with is our current HP 5th G ML370, great machine, had no problems at all running Linux and meeting our needs so far.
I've realised however that it may be one of those times where I should "speak now" if I think I might need more kit.
I've also just bought in a Dell 1950 for development but may have to reconsider it's purpose.
Considering moving the front end(s) onto it and dedicating the HP to our database(s).
This still may not be enough.. so responses such as yours help matters a great deal.
________________________________________
From: Virtual Learning Environments [[log in to unmask]] On Behalf Of Harrison Tim (Staff) [[log in to unmask]]
Sent: 16 May 2008 12:10
To: [log in to unmask]
Subject: Re: [VLES] System Resources & User Impact
We tried running Moodle on a single system (web and database/files) but
could not get the sort of performance we wanted. This was particularly a
problem with on-line testing when we needed to have 250 users running at
the same time on a quite long test. The maximum we could get was about
80 using linux/apache/MySQL (Windows gave us about 60). We then moved
back to windows and tried the updated PHP designed for IIS7 which was
far better and gave results as good as the linux versions. We also, at
that point, separated to 3 front ends (load balanced) and one back end.
That worked well for a while but started having issues which we could
not understand. It is possible that the problem was that we were using
the 2008/IIS7 PHP on 2003/IIS6 though it was an official Microsoft
adaption. We then went back to linux/apache and used the same
configuration, 3 front and one back (database/files). All of these are
virtual servers running on VMWare and connected to a linux based SAN.
This has proved to be the most stable and fastest so far and I will
stick to that until something else goes wrong. If we need more speed we
can just add another virtual front end. The back end seems not to take a
lot of hits. We have been looking at putting in some fault tolerance for
the back end by using some replication technology but this has not
proved too successful with MySQL. MS SQL2005 is much easier to configure
for that type of usage. It is also interesting to me that both the IIS
and Apache web servers have crashed on one server without the others
noticing resulting in some lost logins. The idea that if one goes wrong
the others will take over only works when something significant happens.
I have had the same problem with PIX firewalls. Pull the plug on one and
the other kicks in perfectly but there are many cases where a system can
fail and it does not.
As far as file space growth goes, we do not allow student users to store
files on Moodle so it is just the course content that is placed on the
system by staff at the moment. We have 5T of storage on out linux SAN
using iSCSI connectors so space and is not going to be an issue. If we
get full I will just add more as should any IT support unit these days.
We are replacing our home made SAN with a Clarrion unit in the summer
giving about 20T storage.
If we purchased the hardware we use just for the VLE then it would be
prohibitive but the VLE is just another application (like SharePoint,
Exchange etc.) that runs on a virtual machine. If we need more machines
then we just add another server. I have a pile of old servers we no
longer use because of virtualisation so I can add new ones quite easily
though I prefer the nice new Dell ones.
In terms of staff costs, dealing with linux has been very, very
expensive in time as we do not have the expertise (or perhaps did not
have). We have found all sorts of compatibility issues with the various
components we have used. Most have been documented somewhere but took
hours to find and did not always have a solution other than to start
from scratch with a different version. I am lucky in having a very
professional group of support staff who have worked well beyond their
contractual obligations to get everything working. We have not had any
downtime on our Moodle site despite the changes.
The current trend of Colleges moving to virtualisation and SAN usage
means that they are in a much better position to cope with change but 5
years hence is beyond my ability to predict. I think I am safe for 3
years unless something major happens. I was at Microsoft in Reading a
couple of days ago and their future intentions seem to fit into our
model and we are 95% Microsoft anyway.
Tim
-----Original Message-----
From: Virtual Learning Environments [mailto:[log in to unmask]] On
Behalf Of Gary Day
Sent: 16 May 2008 09:41
To: [log in to unmask]
Subject: [VLES] System Resources & User Impact
Sorry, tried to send this last night and realised I hadn't received
confirmation mail.
Hello, newcomer to the list.
My name is Gary Day and I'm VLE Developer at Weston College.
I have a few questions for VLE Devs/Admins.
We are currently running Moodle on a single box configured for both
network and Internet access, the time has come when I'm starting work on
a rebuild, a rebuild that moves us out of our year long trial and error
period, away from the bleeding edge of Fedora and applying updates and
hoping it won't keel over and into a more Enterprise way of thinking.
Moodle will no longer be the start and end of our VLE, it will be a
component of a VLE made up of various applications and services.
I'm pretty much addressing this to anyone serving up their own system on
their own gear but any feedback would be great.
How big is your school/college/userbase?
What are the most "resource hungry" areas of your inst. in terms of
hardware, database "growth", memory, disk space etc?
Are you dedicating machine(s) to your database(s) and serving up the
front end(s) from another (possibly virtual) machine(s) and if so.. has
this proven to be cost effective in terms of initial hardware costs and
maintenance time?
On the other side of this, has it proven to be excessive?
Basically, why are you making the choices you are making and were/are
they the right choices (based on your userbase/resource consumption)?
Do you believe you have made reasonably "future-proof" decisions (let's
say a future five years from now)?
Thanks, in advance for any time spent on this request.
Gary.
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