Virtualization in more detail

Virtualisation, Physical Servers and Virtual Servers

Virtualisation

Virtualisation software technology encapsulates all the software necessary for a server - the operating system and applications, space for log files and metadata, and all user data - into a single file on a disk of a physical server.

A physical server is just about what you would expect: a metal case containing a power supply, motherboard, CPU, memory, and disks. This physical machine is the virtualisation host computer, and it runs a special control layer to manage multiple virtual machines which do the actual work of providing services to users. The physical host server only takes care of the underlying housework to run the virtual machines: sharing the physical resources of the physical host server with different virtual machines running on it.

A special Web-based interface running on the physical host allows authenticated administrators to control the virtual machines. Administrators can shut down or start a virtual machine, configure it with more or less disk space, memory, or CPU cores, take snapshot backups, or even migrate the virtual machine from one physical host to another.

From inside the virtual machine environment, it looks like it is running on normal hardware, and sees the number of processors, the available memory, and available disk space that it has been assigned by the controller software on the physical computer host.

This physical server can be located on a server computer in your office premises, or it can be a physical server in a datacenter anywhere on the planet. Your server's virtual machine runs on one of these physical servers, and can be migrated between different physical host servers.

Virtual machines and physical host servers

The virtualisation technology used by Words and Wires runs under the Proxmox Virtual Environment, and is based on KVM for the virtual machines, running Debian Linux for the underlying physical host operating system. The virtual machine servers Words and Wires provides run Ubuntu Linux, the most recent Long Term Support (LTS) server release. The entire software stack is entirely Open Source, so that your virtual servers can be copied, cloned, and migrated from one physical host to another with no license cost issues. Moreover, the physical server can run on just about any recent Intel hardware, from midrange desktop material to top-of-the-line multiprocessor servers, using entirely Open Source host software with no licence costs whatsoever.

High Availability

Physical hosts can even be connected together over the network into High Availability clusters, to share resources and virtual machines. This requires a very high-quality network connection, so it can only be done between local servers in your office, or between servers in different datacenters, not between local servers and datacenter servers.

Asynchronous Replication

In addition to High Availability clusters, Words and Wires has developed a much more flexible and lower-cost alternative: asynchronous replication. We copy your full virtual machine to a remote backup server once, and from then on we only copy the changes to your virtual machine to the backup server. Depending on the network connection, we can run the incremental copy hourly or daily. Then, in case of failure of the main machine, the changes are restored to the original full image copy, and this backup virtual machine is started on the backup physical host server. Then your virtual machine is up and running with all the data from the last backup.

Recovery from physical host failure

This means that your virtual server can be migrated from one physical host server to another in a matter of minutes or hours, limited only by the speed of the network between them. The impact this has on your data security is directly measurable, even if you run a local server in your office: assuming nightly backups to a warm failover server, you can be guaranteed to have a running server with all your data within 1 business day of a disaster, including hard disk crashes or damage to the physical server. If your virtual server runs in our datacenters, the time to switch to a datacenter backup is even shorter.

Different virtual servers for different services

Virtual servers also allow you to run different services, aimed at different audiences, on the same physical machine. For example, if you have a physical server in your office, the network firewall can be on a virtual machine, and route traffic between the Internet, the LAN with all your local users, and the virtual servers running on the physical host. Or a file server can serve files only to client computers on the LAN, inaccessible from the Internet. You can have an entire Internet infrastructure, with separate firewall, mail server, and fileserver, on a single physical machine. And you can purchase this entire IT infrastructure-in-a-box to run in your office starting from less than a thousand euros, or we can run it for you in a data center for one hundred euros per month.

Different virtual servers on different physical host servers

Or you can split your services into separate virtual machines, and then run your virtual servers on different physical host computers. For example, you can have some machines running on your server locally, like file sharing and firewall, while running your email server in a datacenter, for ultra-rapid Internet connectivity.

Virtual server capacity

Your virtual machine can have an unlimited number of users, redirects, files, calendars, and mailboxes. Around 2-50 users is reasonable, but there are no technical or license restrictions. For datacenter-hosted virtual machines, the total data space for a Private Cloud and Email server is 100GB. For virtual machines running on a computer in your office, the €995 base machine can host around 200GB on SSD and 2TB on magnetic hard drive, and for less than €500 more, you can easily handle up to around half a terabyte on SSD, with over 4 TB on magnetic hard drives.

Whatever your choice, local or in the datacenter cloud, Words and Wires has a cost effective solution for your needs.

Where should you host your Virtual Server?

Hosting in your office

Imagine this situation: you have 20 people working in a series of offices with good wiring and a fast local network. Most of your work involves sharing files and intra-office emails with large graphics. You run a server in your office.

Advantages

very rapid access to local files and email
very rapid transfer times for big local files
abundant cheap, fast local storage available

Drawbacks

slower to send large emails to multiple remote recipients
slower to share files with remote users
cost of purchasing and maintaining server hardware
remote sharing speed is limited by the office Internet connection

Datacenter hosting

In this scenario, your organisation consists of two people who work in an office, and 20 people who work from their home or while traveling. You need secure email and file sharing services for office documents, brochures, and photos. You run your server in a datacenter.

Advantages

rapid email reception to all users
rapid email sending to multiple remote users
rapid file sharing for remote users
transfer speeds depend only on the user's own Internet connection

Drawbacks

slower file transfers between the two office computers
more limited storage available: max 100GB for email + files

Combined local and datacenter hosting

If you have two different requirements for two different staff groups, like a 20 person office staff with 30 sales representatives on the road, a two-tiered approach could work better: a local server for local file sharing in the office, and the email server in a datacenter.

Advantages

reasonably rapid email reception to all users
rapid email sending to multiple remote users
very rapid access to local files and email
very rapid transfer times for big local files
abundant cheap, fast local storage available

Drawbacks

slower to share files with remote users
cost of purchasing and maintaining server hardware
remote sharing speed is limited by the office Internet connection

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