why i like virtualization (and why hardware sucks) _ bob plankers, the lone

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I Like Virtualization (And Why Hardware Sucks) : Bob Plankers, The Lone Sysadmin

lonesysadmin.net/2007/06/18/why-i-like-virtualization-and-why-hardware-sucks/[1/19/2011 5:41:50 PM]

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Why I Like Virtualization (And Why Hardware Sucks)By Bob Plankers on Jun 18, 2007 in Featured, Virtualization

I was asked why I like virtualization and why chroot jails arent a better way to do

things, at least on UNIX-like OSes. To figure out why I like virtualization, lets start

with what I dont like about hardware:

Failures. Something is always going wrong, whether its a fan, disk,

power supply, etc. More servers means more failures. We buy

warranties to help with this, but warranties cost money. It takes timeto deal with failed components, too.

Firmware. It is hard to update firmware levels. Every device is

different, and a bunch of update methods end up requiring you to go

out to the box with a USB stick or a floppy disk. That takes a lot of

time, usually at times of the day Id rather be somewhere else (like

sleeping).

Cables. I hate cabling. It costs a lot of money, a foot at a time. It gets

tangled. It gets unplugged. It gets mislabeled. It takes a lot of time

and vigilance to do right.

KVM. My KVM system is IP based. It uses Cat5 cable and has USB

dongles that attach to the hosts. It costs a ton of money. The dongles

have strange incompatibilities which make it an adventure to connect

a server. Its also another cable to manage, another system to

maintain, another drain on your time.

Racks. Racking a server means I have to go to my data center, whichmay not be in the same building or city as me. I have to worry about

available rack space, power in the rack, and cooling. I have to worry

about two post or four post racks, which type of holes in the rack, and

whether I have the right screws. Racks cost a lot of money, too.

Power. I hate power cords. They get tangled, messed up, unplugged.

We order short power cords to help with that, but those cost money.

To keep things running we have a UPS. UPSes are expensive and

require maintenance. Speaking of money, I hate paying power bills,

too.

Cooling. Cooling requires equipment, which in turn requires

maintenance. It also requires power. Maintenance and power require

money. Did I mention that I dont like giving other people money? I

want to keep it and buy myself cool things. :-)

It basically comes down to money and time. Time is really money, though, becauseto get more time you have to hire someone to help.

So how do you reduce these costs? Simple: have less hardware. Why cant we have

less hardware?

Applications arent good at sharing. They require specific versions of

other software, different from what the other applications require. For

example, an application written in Perl might require DBD::Oracle

1.14, another 1.19. Now I need two different copies of it and it isnt

simple anymore, especially if the applications assume that DBD::Oracle

will be installed in /usr/lib/perl5.

It can be hard to figure out performance problems on a machine that

is doing a lot of different things.

It is hard to tune a machine for performance with multiple different

applications. Do I tune for Apache or MySQL?

Customers have wildly different security requirements.

Customers have wildly different maintenance window needs.

Customers want to build clusters. How do you share a cluster with an

application that isnt clustered?

Customers just dont want to share. They dont want anything to do

with another project or customer. They want their own machines and

want to have their way with them. Coordination between customers is

sometimes impossible.

Customers want separate development, test, QA, and production

environments. They want to be able to do load testing and other crazy

things without impacting or being impacted by someone elses

software. Unfortunately, development, test, and QA environments will

sit mostly idle over their lifespans.
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Approaches like chroot jails are great for single, well-known applications. The more

applications you need to run in a chroot jail the harder it gets to maintain, though.

You end up needing second, third, fourth copies of libraries, binaries, etc.,

especially if youre trying to chroot interactive users. Automatic patching processes

like yum, up2date, etc. dont update your jails so you have to do that manually.

The jail doesnt address things like differing maintenance windows, or any of the

non-technical problems of sharing a machine. This approach may have performance

benefits, but to be honest performance is usually not a big factor.

Most of the problems in sharing a machine are actually problems with sharing the

operating system. Virtualization decouples the hardware from the operating system,

and because of that we can solve all the problems of sharing a machine by choosing

not to share at all. No chroot jails to maintain, no worries about versions ofsoftware, no endless coordination meetings just to schedule a reboot of the server.

So why do I like virtualization? It lets me get rid of hardware but doesnt force me

to manage complex situations that arise from a shared OS. For the operating system

it is business as usual, which means relative simplicity and well-understood

processes. I like that.

Related Posts

1. Why VMmark Sucks

2. Keys To Virtualization Success

3. Vendors Who Dont Realize Virtualization Is Here To Stay

4. CIHost Sucks and I Need Another Host

5. Vista Officially Sucks

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6 Comment(s)

By Ian on Jun 19, 2007 | Reply

Excellent post. For my situation, seeing as I work for a K-12 school district, its

very difficult to justify the up front costs for virtualization. Between the

hardware costs for a beefy Dell 6000 series box and the high costs of licensing

Vmware, its too much for my situation. If our district was twice the size it is,

we would be getting to the point where virtualization might be doable.

My only real option is to wait and see what Novell does with Xen in the next

couple of years. That might allow me an avenue to explore the technology and

save some bucks on power and cooling. Im maxing out the cooling right now

with one rack of servers and we managed to blow a 20 amp fuse out earlier this

year and all of our machines lost power when we tripped the breaker on the

generator.

Sorry for the rambling ;)

By pooya on Jun 19, 2007 | Reply

Thanks Bob. Very nice article. I dont know about the state of the current

virtualization softwares. If the open-source and free (Xen/QEMU?) ones are good

enough and whether they support migrating a live system to another machine. If

they are already like that then thats awesome.

By nickyp on Jun 20, 2007 | Reply

Pooya: Xen is pretty good and reliable. I trust a vendor like Redhat to provide us

with a good (and stable) Xen environment.

Live-migration is supported, but that requires some kind of shared storage and

sometimes even supports booting from a shared drive, so the hardware can

remain diskless.

But shared storage management will make the deployment more complex of

course. But youre reading the Lone Sysadmin and already know that ;-) Another

issue is that only one shared storage node becomes the single-point-of-failure

for all your VMs. How do you treat this SPOF in your environments Bob?

I guess everything has its pros and cons.
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By Bob Plankers on Jun 20, 2007 | Reply

Right now storage is the Achilles Heel of virtualization. There is no way around

your storage as a single point of failure :-(

By pooya on Jun 20, 2007 | Reply

Well, I guess in theory storage can also be distributed. Hmm.. what was that?

Coda? Lustre? I should look into them to see if therere reliable.

By James Grinter on Jun 22, 2007| Reply

Ive just starting reading the short paper, about cooling-efficiency, being

presented at Usenix this week [Cullen Bash and George Forman: "Cool Job

Allocation..."].

They suggest some neat ideas, for future data centres, such as moving around

VMs to dynamically migrate jobs to improve cooling efficiency.

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