Basic VMWare Question

Guest2

Guest2

Guest2

Soldato
Joined
6 May 2009
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In the future we are looking at changing to VMWare and using vSphere, with maybe 4 servers with ESXi on. At the moment I am just about to test VMWare and know very little about it other than the following (which may or may not be 100% correct)...

VMware ESXi - Install this onto a blank server. Acts as resources

vCenter Server - Central administrator for ESX/ESXi hosts connected on
a network. Used to created a cluster of ESXi hosts where the resources are linked

vSphere Client - Installs on a Windows machine and is the primary method of interaction with VMware vSphere. The vSphere Client acts as a console to operate virtual machines and as an administration interface into the vCenter Server systems
and ESX hosts.


At the moment my test setup is as follows...

HP Proliant DL120, 4GB RAM. VMware vSphere Client and vCenter server installed
I planned on putting ESXi on an old dell workstation but I now see it needs at least 2gb ram amongst other hardware. So I will move ESXi to the DL120 and install vCenter Server and vSphere on a workstation if possible

Can vSphere be installed and work correctly on the same machine as vCenter Server?

I have just been reading the following documentation

"After you install vCenter Server and the vSphere Client, you can configure communication between them. This chapter includes the following topics:..."
 
You're nearly there. vCenter is a central management system, it doesnt necessarily create the clusters, but enables you to do so with the correct modules.

DRS is one such module, that migrates machines in real time (using vMotion) onto different hosts in order to balance the load. HA (high availability) is another option, that restarts the guests on different hardware if a host dies. Finally, Fault tolerance keeps multiple copies of the same guest running in sync on multiple hosts - allowing seamless failover if hardware dies. All these require vCenter, but it's not the only component.

vCenter is a Windows application, I assume when you ask if it can be installed on the same machine as vSphere, you mean on the same machine as ESX? vSphere is the name of the entire package, not a single product. As ESX/ESXi are bare metal hypervisors, you cannot install vCenter on the same physical machine. However, you can create a virtual machine on an ESX host for your vCenter server - this is a supported configuration now, previously it had to be a dedicated physical box.

There are pros and cons to a virtual vCenter server - the pros are the usual virtualisation pros: cost effectiveness plus being subject to the aforementioned DRS/HA etc if you choose to do so. vCenter needs to be running for DRS to function, but not HA - vCenter is only needed to configure it. So if you have a virtual vCenter machine and the host it is running on fails, HA will reboot it and then DRS will rebalance the load when it boots up again.

Remember, for all of the interesting stuff to work, you need shared storage

Quite complicated, but hopefully that's at least semi-clear!
 
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Thanks for the help.

Thats where i'm getting confused, I installed vSphere on the Server and presumed it was just vSphere client. When it really is vCenter too, right?

HA and DRS on enabled on the cluster i have created. My next stage is to get a hypervisitor setup, but i think i might have to put the hypervisitor on the server and install vShere on an old workstation (which probably wont install anyway as it will need 2gb ram % other hardware)

I was reading this article yesterday. Seems you can just about do anything on virtual hardware. This is where it gets even more complicated...

VMware ESX 4 can even virtualize itself

http://www.vcritical.com/2009/05/vmware-esx-4-can-even-virtualize-itself/
 
vSphere client is the client software - you can use it to connect to a vCenter management server or directly to an ESX/ESXi host.

As I said above, you'll need some sort of shared storage (iSCSI/Fibre Channel/NFS) to make use of DRS and HA
 
Yep on vSphere client i can see VMWare vCenter server 4.0.0.
When I right click on the cluster and go to edit settings I have HA and DRS both ticket.

Next step is to get ESXi on a machine I suppose. I'll report back when this is done

Because I am working with little resources here, I will probably go down the router you mentioned. I.e - Wipe the DL120 machine with vSphere on, install ESXi on the Proliant DL120 then setup a virtual machine for vSphere, then put the client on another machine.

Or do you also run the client from the virtual machine with the ESXi machine?

Thanks for the help
 
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You'll be able to create a cluster, but you wont be able to do anything with it without 2 machines connected to the same SAN and a vmotion network configured.

I just run the client from my PC
 
Really?

Looking my mates setup at his work, hes got the main vCenter then 4 ESX servers linked to make one cluster. Then hanging off the 4 ESX servers are another 12 odd virtual servers.

I thought you just need to setup the ESX/ESXi servers on the same network as the vSphere/vCenter installed then add a host from the wizard and select the ESXi server. Whats all this about SAN and vMotion?

On vSphere...

Select cluster > add a host > enter ip address of host to add to vCenter > press Next...???
 
What are you expecting to achieve from a cluster?

A vSphere cluster can consist of High availability or DRS, like I said above. DRS uses a technology called vMotion to move VMs between host in real time. HA instantly powers up failed VMs on other hosts - both of these things require shared storage (a SAN) in order for all the hosts to be able to see the image files. The technology behind vMotion is quite complicated - but think about it from the HA module's point of view. 2 servers, if your VMs are stored on the HDD of Server 1 - how is Server 2 meant to start that machine up when Server 1 bites the dust?

A cluster isnt a magical sharing of host resources, it's a way of enabling these features

You can use vCenter on standalone hosts and make them appear in one folder/cluster etc, but its not actually going to do anything over and above standalone ESX servers
 
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I thought the cluster is just a group of hosts where the hosts resources become part of the cluster. So if we have 4 servers we need to pool their resources for the VMs to share.

I read that it enables HA and DRS but cant find anything about vMotion or SAN mentioned, at least in the wazard and cluster options

Ta
 
As above - a cluster ONLY enables those options, nothing more. You can't pool resources together like that - the closest is DRS which balances load between them.

DRS uses vMotion to move the servers - although vMotion can also be initiated manually for maintenance etc. vMotion requires shared storage, as does HA - the wizards dont mention it because they assume you've researched it properly before you try and set it up :p

As I said above, think about it - how do you reasonably expect these features to work if the data is stored locally on each server?

All you'll achieve by creating a cluster in an enviroment without shared storage is a slightly different view of the virtual machines (in a non cluster they appear under the host, in a clustered setup they appear under the cluster)
 
What he said ^^

You would need to create a bunch of iSCSI shared storage accross all hosts at the bare minimum to enable DRS/Vmotion.

Id like to see ESXi come with free iSCSI SAN software out of the box for uber all in one much cheapness HA ability.
 
you can of course create yourself a virtual SAN :P

Openfiler have a nice appliance that allow you to present storage as iSCSI and allow you to play and test such things without having to shell out for a san.

there are also a number of NAS products that will do the same thing.

I have an iomega IX4 200d stor center 4tb NAS that has dual gigabit and is VMware approved. it has iSCSI targeting etc.
 
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