[ubuntu-uk] Redundency was Going back to the Dell deal...
softy.lofty.ilp at btinternet.com
Mon Sep 10 21:56:56 BST 2007
One question though. I've seen on the various clustering projects that they
all offer a type of load balancing so why not go for a software solution as
opposed to a hardware one?
Nevertheless, thanks for answering my question.
From: ubuntu-uk-bounces at lists.ubuntu.com
[mailto:ubuntu-uk-bounces at lists.ubuntu.com]On Behalf Of Mark Harrison
Sent: 10 September 2007 11:01
To: British Ubuntu Talk
Subject: Re: [ubuntu-uk] Redundency was Going back to the Dell deal...
We have a five-server cluster.
2 off, webheads 
2 off, database servers 
1 off, "spare box" 
At the moment, all the traffic is going to one of them, but the other is
kept updated (rsync is your friend.)
The Plan [TM], once we get more traffic / income, is to put a hardware
load balancer (pair) in front of the pair, and split out the traffic
between them anyway. Hardware load balancer tend to give the twin
benefits of resilience and performance.
 Database servers:
One of them is live.
One of them is "backup" with, sort of, MySQL replication between them.
If the live one were to crash, I'd go in, change the file on the
webheads that tells them where to find a database server, and start with
the backup in seconds.
- The file on the webheads is NOT in /var/www it's in /var/<something
else> and included in code. Any pages that need to access the database
have an include("connection.php")... that file reads:
$dbip=fgets(fopen("/var/<somewhere>/<ip address of database server
.... and then goes on to run the appropriate MySQL database commands,
returning a connection.
- MySQL replication doesn't work reliably, so every week, we go in and
re-create the backup database by hand. I'm almost tempted to write a
script file that does this hourly!
 Spare, spare, box
This sits with Ubuntu, MySql5, Apache, and PHP pre-installed, but NO DATA.
When (if) a server crashes, the plan is:
- 1, make the appropriate backup box live  or 
- 2, copy either the application, or the database onto the spare, spare,
box... and make THAT a backup box for the one that had failed.
- 3, try to work out what had gone wrong with the live box
Ian Pascoe wrote:
> Mark et al
> When you say you have a spare box lying around waiting for a catasrophe to
> happen, is it literally tucked away in storage somewhere, or is it
> pre-connected to the farm but just powered down?
> The reason I ask is whether you physically alternate the backup box or
> power up / power down one box sequentially in the farm at predefined
> -----Original Message-----
> From: ubuntu-uk-bounces at lists.ubuntu.com
> [mailto:ubuntu-uk-bounces at lists.ubuntu.com]On Behalf Of Mark Harrison
> Sent: 07 September 2007 21:23
> To: British Ubuntu Talk
> Subject: Re: [ubuntu-uk] Going back to the Dell deal...
> Michael Holloway wrote:
>> 2. How many Linux users would buy a one? I'm not sure i can answer this,
> but i imagine not too many. Most linux users like to customise their
> machines, and put all the latest and greatest (or cheapest and oldest)
> compenents into it.
> 10 years ago, that would have been me. In fact, about 10 years ago I
> _did_ build my Own PC (a Pentium-90 in fact.)
> Now, I want a machine that works, with an operating system that works.
> Don't get me wrong - I work in IT, I'm into the latest toys as much as
> the next geek, but desktop O/Ss aren't an exciting playground for me
> compared to Ajax apps :-)
> As I said, I want a machine that works, with an operating system that
> works. Hmm... let me think? Should I go with (out of date) XP? Should I
> go with (utterly, cripplingly slow) Vista? or... can we think of another
> O/S that might run a lot faster on modern laptop hardware AND be more
> I'd be INCREDIBLY tempted to go with a pre-installed,
> manufacturer-supported, Linux-laptop next time round.
> Mainstream buyers have a different mind-set, and the "Dell with Ubuntu
> pre-installed" is hitting a lot more of those buttons than "download
> this distribution" ever did.
> The worst case is that Dell do the work (or get Canonical to) to come up
> with a standard image for their Ubuntu laptops, and that image sits on a
> server farm in Ireland not being installed from much. Net cost to Dell,
> a small amount of disk space. Net benefit to Dell, marginal increase in
> customer choice.
> Marginal benefit to Ubuntu - huge - endorsement from Dell that our
> chosen distro is supported by the biggest and the best. (Yes, I know, HP
> / IBM / RedHat, but heh... Dell has the biggest mindshare for desktops /
> laptops, I suspect.)
> And, for people like me, who are already on pure Ubuntu-servers at work
> (4 in the operational farm, 2 development servers, and a spare box
> sitting around to swap in in the event of catasrophic hardware failure),
> this has a marginal benefit to ME even if I never buy a Dell Linux
> Laptop - it helps convince my board (who to be fair, I've trained to
> trust my technical judgement) that I am backing the right horse with
> ubuntu-uk at lists.ubuntu.com
ubuntu-uk at lists.ubuntu.com
More information about the ubuntu-uk