Silly question

slee335

i'm studying for the vcp5 and i'm wondering why would you need to have so many hosts. i know its a silly question why would you need a 100 windows server and linux box, what else do you virtualize?i was just wondering since i'm new this.

Lexluethar

More Hosts = More VM's.

You can only fit so many VM's on one Host depending on how much RAM and CPU cores the Host has.

The more VM's you have in your environment, the more Hosts you will require or the more powerful the Hosts need to be.

There is a delicate balance between putting as many VM's on a host as possible to maximize your efficiency while ensuring VM's do not have performance issues.

slee335

I mean vm not host. Just curious what you kind of virtual machine you guys are creating. Ex windows server, linux, what else

TheFORCE

slee335 wrote: »

I mean vm not host. Just curious what you kind of virtual machine you guys are creating. Ex windows server, linux, what else

It all depends on the business needs and what the best tool for the job is. You can have load balance servers, forwarding engines etc. Depends on your needs, usage and denand

Lexluethar

The company i work for has around 450 virtual machines. Realize a virtual machine is just like a normal server, so for every business function you will have a virtual machine (or mulitple).

This you have a Domain Controller for most environment, DHCP server, PKI server, appliances for security and other functions, every application you use probably has it's own server unless it's really small. Email will have at least 5 servers depending on what version and the size of your company. Print servers, file servers, ect ect. I could go on and on but you get the point.

joelsfood

Items that can't coexist on one server (ie front and backend database, Exchange roles, etc). Load balanced servers for availability. Different security requirements (multiple internal clients all have web servers that they need admin access to, but can't have access to each other's servers). Different applications (AD, Vcenter, SQL, Exchange). Virtual appliances (Nexus 1000V, F5 LTM, vMX, vSRX, Vcenter, VCoPs, etc)

TheProf

slee335 wrote: »

i'm studying for the vcp5 and i'm wondering why would you need to have so many hosts. i know its a silly question why would you need a 100 windows server and linux box, what else do you virtualize?i was just wondering since i'm new this.

Very large organizations run a lot of applications!

Installing all these applications onto one VM is not a good practice nor do some apps support coexistence with other apps.

VM = Server

We deploy VMs to either run applications or services

DoubleNNs

So that is the OS crashes, only the features on that particular VM goes down.
i.e. Marketing VM, Accounting VM, HR VM. Marketing VM goes down, and both Accounting and HR department are unaffected while you work on the problem for Marketing.

Easier to install different versions of software.
Ops wants Python 2.x for scripting. Dev wants Python 3.x to work on their new application. You could technically muddle around to get both installed and working on the same VM, but easier to split them out.

Clusters & scalability.
You can have 4 VMs in your cluster this month. Then add a 5th VM to the cluster next month. You don't need to resize/reprovision each individual VM.

Diff OS Versions
Some applications may be easier to set up on Ubuntu. Other legacy apps may only work on Server 2003. A Dev might be testing out CentOS 7, even tho the organization typically uses CentOS 6 as a standard. A specific team might use Solaris. You would need a diff VM for each diff OS and each diff OS Version.

Redundancy
Not for scalability, but you have 2 servers w/ the same functionality. One of them lives on a server w/ hardware failure. Or the OS simply crashes. You have a backup to take it's place.

I don't actually have much virtualization experience, but I would think these would be good use cases. Just what I thought up off the top of my head at the moment. Additionally, Understandably, each point above is extremely simplified. I think it's a good question though, and one that I myself try to understand as I make the transition into Systems Administration.

paul78

Not a silly question at all - you would be surprised by the number of VM's that large enterprises have. We have probably around more than 15-20 thousand VM's spread across multiple data centers.

TheFORCE

paul78 wrote: »

Not a silly question at all - you would be surprised by the number of VM's that large enterprises have. We have probably around more than 15-20 thousand VM's spread across multiple data centers.

What! You working for Netflix?

paul78

TheFORCE wrote: »

What! You working for Netflix?

I work in one of the segment of financial services.

I imagine that Netflix probably has more - they have a much different use-case. Also Netflix is built on AWS and is architect-ed with some interesting elastic capabilities.

VM sprawl is a real problem at large enterprises. And when you factor in testing and development environments, the number of VM's can add up quickly.

TheFORCE

paul78 wrote: »

I work in one of the segment of financial services.

I imagine that Netflix probably has more - they have a much different use-case. Also Netflix is built on AWS and is architect-ed with some interesting elastic capabilities.

VM sprawl is a real problem at large enterprises. And when you factor in testing and development environments, the number of VM's can add up quickly.

Yeah I heard abouy some interesting ways that netflix is using AWS. I beleive their DR is alwats on, that's why you never get any service interruption from them.