Plesk-based hosting can often suffer from a resilience problem: failure of the DNS for sites it hosts if the server goes down for any reason.

Ideally a zone should have a number of domain name servers located in different places. A zone is basically a domain and all its sub-domains. The zone record tells other servers where to find everything for that domain – where the websites are, the main servers etc.

Plesk run on a server or virtual server (VPS) generally provides two name servers. They will be configured automatically when websites are set up on the server, and are very convenient to use. Plesk also allows some customisation of the domain records so that, for example, a sub-domain can point to another server, or the mail server points to your office server.

The problem comes when the server running Plesk is down or inaccessible. A mail server trying to send an email to your domain will suddenly find there is no record anywhere of that domain – it has basically dissappeared.

The way around this is to use external name servers. By setting up the external name servers as a slave servers, they can be made to automatically keep themselves updated from your master name servers on your hosting machine.

For our domain, I used www.zoneedit.com to set up a slave for one of our zones. The slave was pointed at our hosting server (using its IP address) and that was it for that end – the zoneedit slave just fetches updates when it is appropriate and updates its own records, putting them onto two geographically-separated name servers of its own.

Back to the domain registration settings, I then needed to add the zoneedit name servers to the domain, giving me four in total (the two on our Plesk hosting and the two on zoneedit). There is no priority assigned to any of these name servers, so a server looking for our website or mail server could go to any of these sources. It is therefore very important to ensure they are all synchronised identically.

One last step was to tell Plesk to allow these name servers to fetch a copy of the zone records. This is not so obvious but is in Plesk under the option:

Server -> DNS Settings -> Common ACL

In here I added the IP addresses of the two zoneedit name servers assigned to my zone, and then the updates simply went ahead.

You can test this works using nslookup command from another server. Create a new sub-domain, then check it can be seen on your Plesk server:

nslookup new.sub-domain.example.com ns.plask-server.example.net

Then try the same command but pointed at the external name server. You will find the external name server cannot see the sub-domain immediately. Try again in an hour – and it should be there. If not, check your setting and TTL etc.

Hopefully that will give you more resilience; even if your website is down, other severs that your zone points to are still locatable.

One thing that I am still looking for a solution to, is domain aliases. A domain alias for a domain set up in Plesk will not get transferred to the slave name server. Even if the alias is a sub-domain of the main domain, it does not get transferred. So the hosting server will correctly return the IP address for example.com for the alias myalias.example.com, but the slave name servers will not. This is not just a problem for when your hosting server goes down, because there is no priority on the name servers – all and any could be used at any time for a server to locate your alias domain, and depending on which name server it hits, it is pot luck as to whether it finds it or not. I’m looking for a solution to this, so any hints appreciated.

I’m also looking for a decent and cheap slave name server service. zoneedit is good and reliable, and easy to use, but could get costly when we have scores of domains to sync up. Any suggestions?

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This is something that has been bothering me on the odd occasion for years. It is intermittent, so is something I have been able to live with, but it would be nice to get to the bottom of it.

Basically, there is a key combination – somewhere around the “A” on my keyboard, probably involving the control and perhaps the shift keys, and is so easy to accidentally press when not being careful, that locks up all my keyboard input.

When I say “locks up”, I mean that the keyboard becomes completely unresponsive. Nothing gets it back, except a full reboot, and if you know how long my PC takes to boot, you would realise it is not very convenient (I do manage to make a cup of tea while it boots, which is a bonus, kind of).

I have tried unplugging and plugging back in the keyboard. I have tried undocking the PC (I use a Toshiba Tecra laptop in a docking bay). I have tried logging off and on again. Yes, I have tried logging off and on again. None of this works; only a full reboot does the job.

It locks up both the external Logitech keyboard and the laptop’s built-in keyboard, so there appears to be no workaround.

So – what could this be? I have a feeling it is some kind of “feature” that is misbehaving, but cannot think what it could be. I have not even been able to find the key combination purposefully to give me any more clues. It just happens, and when it does I know my fingers were pressing some keys around the “A” end of the keyboard.

I have a feeling I will never find a solution to this. Perhaps I need a new laptop.

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I came across this neat Windows application today. It is basically a tool for creating customised Windows installation disks.

I’ve seen similar tools for slip-streaming service packs into disks, but this one goes a step further and makes it dead easy to include drivers and various other Windows tweaks. It is all very straight-forward to use:

1. Point it at the original Windows disk.
2. Tell it what you want to change (point it at service packs, drivers, etc.)
3. Tell it to generate an ISO.
4. Press GO.

The application will then spit out an ISO image that you burn to CDROM. I’m sure there are ways to install it over the network without burning a CD too.

I found it while looking for a way to reinstall XP onto Dell machine with a SATA device that the default Windows disk did not recognise.

nlite – http://www.nliteos.com/ – a great application for your toolbox.

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Well, not quite silencing, but they can be made a lot quieter.

D-Link DES-1228p

First a brief introduction. The D-Link DES-1228P network switch is D-Link’s attempt to get into the corporate world. I’ve never much liked D-Link equipment purely because of reliability issues, Netgear being my consumer choice. I gave this one a chance for a client setting up a new office.

What makes this switch stand out is that it provides 24 ports of Power Over Ethernet (POE) along with Quality of Service (QoS) and various other features to help manage the network. These are all features very handy for a large building equiped with new PCs, wireless access points and VOIP phones throughout.

The price tag was £200, complete with five year warranty, which is pretty reasonable considering the competition. The price is more like £300 now, and I suspect it has gone up to pay for, err, reliability issues. I guess some things never change (more on that later).

The switch was installed in a 6-unit wall-mounted network cabinet in the front lobby. The noise from it, even through the cabinet, was just too much. Even though the main office was two doors away from the network cabinet, the high-pitched screach from the four full-speed fans was unreasonably loud. The metal cabinet did not seem to make any difference. The load on the switch made no difference either – the fans ran at full speed whether supplying 100W of power to the VOIP phones, or had nothing plugged into it at all.

So, what to do about it? The first thought was to disconnect some of the fans. I decided against this for warranty reasons.

Next I considered sound proofing the cabinet, and that proved to be the right solution.

After lots of research into sound proof tiles and foams, I ordered a couple of metres of this stuff:

DX40F Foam from Studio Spares

The total cost was a tenner, including postage.

The length shipped to me (arriving the next day in a foot-cubed box) was enough to line the two sides and the base of the cabinet. Being foam, air could still flow through it, but the cabinet had wide slots in the base and top anyway that were not covered by the foam. The idea was just to try and catch the high-frequencies from bouncing around inside the cabinet.

It worked like a dream. The cabinet now emits no more than a gentle hiss, while previously it sounded like a Harrier trying to take off up the staircase.

So, if you have a noisy network cabinet in the office, I would recommend giving this foam a try. Obviously avoid covering any of the air holes, but lining the flat surfaces ought to be enough to make a difference.

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Now, on that reliability issue. The switch failed completely after six months of service (this is before the foam). All the front-panel lamps lit red and the unit did not respond to the network.

It was returned under warranty for a straight swap, which arrived after three weeks of waiting. I didn’t need to send the old one back until I got the new one. There was no fuss replacing it, but navigating the D-Link returns website was a nightmare – dead-end links and endless loops all over the place, much the same as their telephone system. I understand they are going through a phase of turning the support over to a new company, so all is in a bit of disarray.

The new unit, when it arrived, was a bit battered and scratched. If I had the time, I would have changed the case over for the pristine case I was about to send off, but I did not get around to it.

The old unit sported a V2 hardware label. The new unit stated it was v1. However, since the insisdes had been changed over for something new, it could have been V3 inside for all I knew. Hopefully it will last longer.

I was told, when returning the item, that this was a known fault affecting many (or all) of these switches manufactured around August 2008. They also say it can be affected by the unit overheating, but – trust me – with four fans going and very little load for those fist six months, this thing could chill your beer, it was so cool.

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I was recently tasked with transferring files from a failed laptop. The laptop kind of worked, but some bad sectors had started to appear in a number of vital system files, so it was very unstable.

This was an old WIndows 98 system, and I could not simply plug in a USB drive, because there were no Windows 98 drivers around for the external USB drives that I had. In the end the disk had to be removed, and connected up to a working machine with a flying lead.

Since then, I have come across Puppy Linux. It seems to be ideal for this type of thing. By booting it directly from CDROM or USB key, it is possible to have a working Linux box in 60 seconds flat. It is then a simple matter of mounting the local drive, plugging in a USB drive, and transferring the files across.

Puppy Linux is not something I have ever come across before, but it is now a part of my standard toolbox. It also looks like the ideal platform for building custom appliances, such as video players and thin clients.

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