Blog RSSAttach a SATA disk to a local XenServer instance.
March 19, 2012Recently, I have been using XenServer to run a small cloud instance, this has been great but there are a few things you can’t just do with the XenCenter GUI. One of these, was to control and manage an extra externally attached hard drive.
There are reasons why you might want to attach a locally attached drive to a XenServer installation, without putting it in as a Storage Repository. In my case I want to back up data to an external drive (attached via eSata). The idea here is to make the XenServer see this drive as as a removable storage device.
Most of my servers use an ISCSI based SAN, but for backups I don’t want to back up to the same device, plus I want to be able to remove and swap the backup around so adding an extra, external disk is the perfect answer.
To get XenServer to recognise the drive, we need to create some extra symlinks in the /dev tree, this is managed by udev when USB and SATA drives are attached.
In my case, my new drive shows up as sdb, so we add the following lines to /etc/udev/rules.d/50-udev.rules – note, you can do this multiple times if you want to attach multiple drives. Once this has been added, reboot your server and you are ready to roll.
ACTION=="add", KERNEL=="sdb", SYMLINK+="xapi/block/%k", RUN+="/bin/sh -c '/opt/xensource/libexec/local-device-change %k 2>&1 >/dev/null&'"
ACTION=="remove", KERNEL=="sdb", RUN+="/bin/sh -c '/opt/xensource/libexec/local-device-change %k 2>&1 >/dev/null&'"
Windows 8 Consumer Preview
February 29, 2012
Microsoft Today have opened up Windows 8 for anyone who wants to test and try the latest version of Windows. This is the consumer preview program and it allows users to download and try a time limited verison of Windows for free.
Windows 8 has been built with touch based interfaces in mind, this is probably the biggest single change since Windows 95 arrived almost 17 yaers ago. The new interface, called the Metro will be standard on Windows 8. It is critical for Microsoft to do well with this, as this is an area they are competing with Apple and Google at, both of who already have established tablet platforms.
It is easy to see more, and even download the trial from Microsoft’s website, http://windows.microsoft.com/en-US/windows-8/consumer-preview
Are you looking forward to Windows 8, or dreading the change?
Windows 8 Logo Revelead
February 18, 2012For the first time since very early versions of Windows, the new logo for Windows is actually closer to an actual Window! Gone is the wavey flag effect and instead we have a simple, blue Window.
Google Chrome’s New Features? Good or Bad
February 10, 2012
This week Google have pushed out the latest version of Chrome, bringing with it security updates and several new features.
One of these features introduced is “Preemptive Rendering”, which on the front of it sounds like it could be a useful thing to get your page visible quicker. However, it had me thinking, from a server /hosting point of view are these pre-loading systems a good idea or not?
Well for a start off, pre-loading content from a server can potentially add extra load for a user who was never actually going to visit your site. Now, Google have said for the time being it will only work on sites a user visits regularly but I’m still not convinced this is a good plan for those sites. Small sites should be ok, however the bigger the site, the more likely this change is going to hurt them.
For a second, they can start to skew your statistics, if the browser starts to load and pre-render more pages than the user actually visits. Advertisers often require accurate figures if you are to include their banners within your site, having incorrect figures could effect your revenue. My guess would be Chrome and Analytics working together, but if you don’t use that combination then you may be out of luck.
Another change added, is relating to security, Google will compare downloads against a known safe white list. If the URL is not in the list or Google can’t work out what the file is, then the URL will be transmitted to Google for analysis. Now this is another featre that sounds good on the outside, but there are some files that Google should NOT know about (direct / private downloads when transfering files between users for example) – Does this new feature mean Google will start to index / read files that it shouldn’t be able to see?
As this feature is enabled by default, and has to be disabled by the user – I can see most Chrome users won’t touch it.
I already know personally that Google Chrome works with Google, I cannot explain how else files on an *INTERNAL* development server (that is locked access to the internet) can actually appear in Google’s Search index – They are still there now too!
When do features become a problem? When does security get thrown away? I’m all for advancements in browsers but I’m not sure I like some of the recent changes.
Reliance on 3rd Party Services – Good or Bad?
January 20, 2012More and more, developers are becoming reliant on 3rd party services to provide data, provide code or enhance the site that they offer. This can be as simple as somewhere else hosting some of your resources, be it simple Javascript libraries, or actual file hosting (via a Content Delivery Network, or CDN).
Now, I can see the benefits on resources to offload heavy items to other services and while those services are up and operational, its brilliant. Saves you money and means you can serve more users from the same hardware.
However, what happens when they do go down? In most cases, your site should still work just missing functionality. Now, in most cases you will be pre-notified if there is likely to be any prolonged downtime to allow you to do something about it.
The thing that prompted this article was the shutdown of MegaUpload by the US Federal prosecutors. They have had MegaUpload shutdown instantly for violating piracy laws, however, sites like this are used for genuine reasons too – the users have had no time to download any files they may have uploaded there and host them anywhere else. The service was just taken straight offline. This has meant that many sites with hundreds of thousands of legitimate files hosted on this service now point to dead links with potentially no way to get the files back.
What would happy to you if Dropbox suddenly went offline? Or another cloud based file storage solution that is out of your control?