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Tagadab | Virtual Private Server FAQs
Virtual Private Servers - FAQ
Here we strive to answer common questions about VPSs. If you have a question that is not answered here, please e-mail firstname.lastname@example.org or give us a call on 0845 155 0217 between 9am and 6pm, Monday to Friday.
- What is a virtual server?
- What are the advantages of a virtual server?
- Are there any downsides to virtual servers
- Which virtualisation system do you use?
- Do I get 'burstable RAM'?
- How many virtual servers run on one host?
- How many IPs do I get?
- What's the difference between Standard and Premium VS?
A virtual server, sometimes called a virtual dedicated server or virtual private server, is a server that looks and acts like a dedicated server but which is actually a partition of a larger host which runs several virtual servers. The virtual servers do not have any hardware of their own but act as if the portion of the hardware allocated to them from the host is their hardware.
The principal advantage is a reduction in cost. Most people using dedicated servers are not in fact making use of all the CPU cycles, all the diskspace or all the memory in their server, but they are paying for it anyway. Virtual servers allow you to pay only for what you actually need.
However there are other advantages - virtual servers can be upgraded with memory or diskpace almost instantly, they can be migrated from one host to another easily and they reboot far more quickly than dedicated servers.
The principal downside is that each server does not get exclusive access to the physical hardware. Although the virtualisation technologies we use are very good at ring-fencing memory and CPU resources all the servers on one host share a physical network interface so you do not get access to the entire 100Mb/s available. If you have an application which requires very heavy network or disk activity a virtual server may not be for you.
We use Xen for linux and MS Hyper-V for windows.
No, neither of the virtualisation technologies we use allow burstable RAM. There are two reasons why burstable RAM is a bad idea: firstly it means that areas of physical memory can be allocated to one server one minute and another server the next - this has security implications. Secondly, if you use burstable RAM your server might later see its memory allocation reduce. This plays havoc with the performance of some applications, particularly databases.
Each host can run somewhere between seven and thirty virtual machines depending on the memory requirements of the virtual servers.
Each server is installed with 5 unique IPs, the first is installed and the other four you can allocate from your Tagadab control panel. If you need any more than that you just need to email us requesting more and telling us why you need them. There is no additional charge for IPs.
Premium VS are the type of VS we have sold since we launched in 2008. They are provisioned on hosts which have the fastest possible disks - SAS disks spinning at 15,000 rpm. The number of virtual machines per host is restricted make sure disk performance is high. These disks are expensive and the cost of providing these VS is high.
Standard VS are provisioned on larger hosts which do not have locally-attached disks. Instead they use network-attached storage (from Netapp).