I've been curious about this for a while. Also, why run multiple VMs? I usually run multiple VMs for, say, one VM is for debugging and one VM is for installing risky stuff. But on a server standpoint, I just can't see it.
Can someone enlighten me please? XD
Last edited by arkhi; 14 Sep 2011 at 19:00.
Hackers. If 1 server is hacked, the infection doesn't spread throughout the network.
Correct me if I'm wrong
I never thought about the cost.. but then again, wouldn't you want a server to be in its full performance rather than sharing the loud with the other VMs?
Also, I think the security reason sounds good.
To keep uptime....
A virtual machine can be copied very easily at a short notice compared to installing a new server with all the software...
In a data center where there are lots of servers working in tandem, if one server crashes, it may affect the overall performance of remaining network. So the affected server needs to be isolated immediately and a standby server should take its place. This is best done using VMs.
Before the VMs, few machines used to take the load and do the job of multiple servers like a windows server having application server, database server etc. and other windows server to host the web server and mail server etc.
In case of any problems the servers used to be down and it used to take long time to either rectify these servers or prepare standby servers with similar services to take their place.
As there is no limit of VMs one can run in a datacenter, multiple servers each serving one function like a application server, a database server, a web server etc. are created as VMs. After fully installing these servers and commissioning them, clones are easily made (as easy as copying a group of files) and kept as standby. (Even multiple clones can be kept as reserve).
So if a server running on a VM gets affected by virus - worm attack, gets corrupted and beginning to operate erratically or come down, a clone of this server can be immediately put in to service and the affected server is isolated and shutdown. As there are clones available for this damaged server, there is no need to repair this server and it can be disposed off (just deleted).
This will reduce the manpower requirment for maintenance of servers and keep uptime.
VMs make the servers like disposable entities which can be used and discarded once they stop working. That is why VMs are ideal candidates for servers.
Also it is easy to deploy multiple servers (in VM form) for load balancing.
Glad I stumbled across this thread, because I just installed VMWare Player a few days ago, and not having any experience with anything like this, I was wondering pretty much the same thing...actually, I was wondering why a server is required at all? However, I can now imagine.
A robust hardware platform allows you to conjure a virtual server out of a cloud of electrons without waiting for some pointy hair to approve a purchase order. It also gives you flexibility in load balancing where heavily used virtual servers can be located on separate hardware alongside less heavily used virtual servers.
One other advantage of virtual servers in a data farm or Website provider is that each client can have their own server without the need, (or expense), of bespoke hardware.
You will often see website hosting companies offer "shared", "Virtual", or "Dedicated" server options in their price lists
We run servers as virtual machines primarily for a few reasons
--consolidation
--lower costs
--reduce power consumption
--reduce cooling needs.
Generally speaking, in the past when a server was purchased, it was always purchased with more CPU power than it needed, it usually had more RAM than in needed and often had additional disk space allocated for future growth. This usually meant that the box usually sat there humming away at about 5% of it's total capacity and wasn't fully utilizing the hardware.
With virtual machines, you are able to take a number of virtual machines and run them all on one piece of hardware and fully utilize the system. It's better to run 1 server at 80% capacity than it is to run 8 servers at 10% capacity in terms of cost, heat, and cooling.
With virtual machines, in an enterprise environment, you have so much flexibility. For example, we run vmware vSphere in our environment and we have a storage area network. Thus, we might have 5 physical servers each connected via fibre channel cards to a storage area network storage device. So, we might run 50-75 virtual machines across these 5 physical hosts. So, lets say a host needs an upgrade (maybe more RAM or new processors). In a virtual environment like VMWare, you can move the VM's that are running on it to another remaining machine (while it's running with no downtime to the customer). You can then put the 1st host into maintenance mode and you can upgrade it, patch it, perform repairs and when ready you can bring it back online and move servers back to it. The key is that all of this can be done without EVER shutting down the virtual machine serving customers or employees. Of course, this does require a storage area network, which can be a $500,000 storage array, or as simple as a free Linux distro like OpenFiler or FreeNAS. You simply need shared storage.
In addition, virtual machines make OS patching a breeze. Before a big patch, you simply click a button and within about 15 seconds, you have a snapshot of the machine. Let's say you load a service pack and then all of a sudden your server just keeps blue screening and doesn't run properly. In a virtualized world, you just restore back to that snapshot and VIOLA..you are shot right back to where you were. No fuss, no muss.
In a virtualized world, lets say that you have a machine up and running...but would like to build up a test lab to test a new version of software. Simple, you just clone the original box and you have an exact point it time copy. You can bring that up on a test network and test all of you want. Once you are comfortable, you can quicky and easily roll it out to production.
In a virtualized world., you can quickly and easily add more storage space to a server. Oh, 40GB wasn't enough, give it 80, resize the virtual drive and VIOLA..you now have 80GB.
In a virtualized world, you can reboot a VM in about 15 seconds. On physical enterprise class servers, the POST process alone can take 2-3 minutes to intialize a bunch of RAM, initialize a SCSI controller, bring the RAID system online, etc. You don't have anything like this to wait for in a virtual world.
In a virtual world, with all of the hardware virtualized...you are not dependent whatsoever on the machine that you run it on. So, in the event of a crash and you have to restore, you don't need to get the same hardware, same RAID controller, etc. Since all of that hardware is provided in a virtualized form, you simply restore your VM onto any remaining VMWare (or other brand VM Server)...and its back up and running. It's totally hardware agnostic.
I haven't installed anything, but vitrualization software, on a physical server in years. The virtual environment is simply faster, easier, more robust, more powerful, more cost effective, quicker to deploy, etc. I can deploy a new windows server in our environment in approx 6 minutes. It's getting rare these days to run any type of real server on iron ( a real physical server).
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