[CentOS] OT: Why VM?

Sat May 28 03:41:41 UTC 2011
Drew <drew.kay at gmail.com>

>>   2. Reduce data center costs by reducing your physical
>> infrastructure and improving your server to admin ratio:
>> Fewer servers and related IT hardware means reduced real
>> estate and reduced power and cooling requirements. Better
>> management tools let you improve your server to admin ratio
>> so personnel requirements are reduced as well.
> Personally, my experience is that, if anything, running multiple
> systems on a vm host measurably increases the administrative burden
> per host.  For one thing, you now have multiple instances to update
> and to keep secure whereas before you had one OS to worry about.  If
> we had tens or hundreds or thousands of servers then yes, I can see
> the benefits.  We, however, do not deal with equipment on that
> scale.

What you have to understand is that administration of a server is more
then just managing updates on your OS. Hardware needs regular
maintenance just like any system. With virtualization you reduce the
hardware maintenance costs, you still have to maintain the OSes as

>>   3. Increase availability of hardware and applications for
>> improved business continuity: Securely backup and migrate
>> entire virtual environments with no interruption in service.
>> Eliminate planned downtime and recover immediately from
>> unplanned issues.
> I suppose that moving VM instances as file systems provides a real
> value by eliminating the setup and configuration required to get
> bare metal to flash up in a usable fashion.  This is in fact the
> only area that I see a real advantage to VM over bare metal
> installs.

This was the biggest selling point for us. I can migrate all my VM's
off one host while I do maintenance on that host. Also, by backing up
the VM's at the host level (includes the VM config as well as the disk
images) I can restore my entire system onto our backup gear at our DR
site and be up in the matter of hours as opposed to days.

>>   4. Gain operational flexibility: Respond to market changes with
>> dynamic resource management, faster server provisioning and
>> improved desktop and application deployment.
> I have no idea how deploying VMs to a company's desktop workstations
> could possibly benefit the firm.,

VMware does more then just virtualise servers. When they mean desktop
deployment they are refering to Virtual Desktop Infrastructure (VDI).
Instead of having 30 PC's spread over the office, you run 30 VM's
representing those desktops and use Thin Clients to access the
desktops. Using a technology called linked clones you can reduce the
maintenance of those 30 PC's down to just a few master images.

>>   5. Improve desktop manageability and security: Deploy, manage
>> and monitor secure desktop environments that users can access
>> locally or remotely, with or without a network connection, on
>> almost any standard desktop, laptop or tablet PC.
> Again, how is this accomplished and what are the advantages over a
> single OS install?  None of the above claims have anything to do
> with VM per se as far as I can see.

This is part of VDI. By having VDI in the rack, you can deploy virtual
desktops to users whether they are in the office or on the road. I've
seen demo's of the software and while it's outside my firm's budget,
it's definitely interesting technology.

In our organization, we had around dozen servers with about 120 PC's.
During our systems refresh last year, we had concerns about our
organizations ability to withstand a failure of certain key servers,
our remote access and accounting servers being among them.

By virtualizing eight of the physical servers (the others are
geographically dispersed so not candidates for virtualization) down to
a single two node cluster w/ SAN, we were able to refresh our systems
for less cost then buying individual servers, and we ended up with a
system that could withstand the failure of a server without major
downtime. And because our backups moved from guest level to host
level, we now have the ability to restore key machines to a backup
site in minutes as opposed to hours.

The other major benefit we realized going virtual was the ability to
test stuff out ahead of time before sending it to production. Prior to
this we kept older servers around as testbed machines for evaluating
new software. Testing software on older machines really isn't the best
way to test a system's ability to perform in production and there was
no way I could justify buying a brand new server just to test some new
software that may or may not have value. In our virtual environment I
can fire of a VM spec'd the way it'd be in production and test it that
way. If it's a dead end a simple delete of the VM and it's gone. If it
has value, we can migrate the VM into production.


"Nothing in life is to be feared. It is only to be understood."
--Marie Curie