Virtualization

[Hightower]

We're looking at implementing a Virtual Backend like this:

 

(see attachment)

 

Sorry for the cruddy diagram. Anyways, I believe Hyper-V does this with Server 2008 but does anyone know any alternatives?

 

I have found Xen but not sure if it does what i want

[somabc]

You want a 'Type 1' Hypervisor -

 

this requires a CPU that has the right virtulisation extensions.

 

Welcome to xen.org, home of the Xen hypervisor, the powerful open source industry standard for virtualization.

Windows Server 2008 Virtualization with Hyper-V: Home

VMware ESXi, Hypervisor for Server Virtualization - VMware

 

http://publib.boulder.ibm.com/infocenter/eserver/v1r2/index.jsp?topic=/eicay/eicayvservers.htm

 

Xen is linux based and might be pretty complicated, I don't know I have never used it . Hyper-V on Windows 2008 seems to work well, and should be pretty easy if you are used to Server edition. VMWare ESXi is now free but it used to be their big flagship virtuliastion software. I would try out VMWare first as a test to see how easy mangemnt is and either Xen (if you prefer linux) or Hyper-V (if you prefer Windows).

Edited September 11, 2008 by somabc

[Hightower]

Your diagram looks like it has 3 OS installs on one server. Is that right because if so, that's not what I'm looking for.

 

I'm looking for one OS (or more) spread (so the work is balanced) accross 2 or more servers..

[CyberNerd]

Xen is pretty solid and has some nice tools now, it will certainly do all you need. There will also be a good migration path for KVM.

here is a good link for a xen setup:

Red Hat Magazine | Automated failover and recovery of virtualized guests in Advanced Platform

[localzuk]

That isn't virtualising, that is clustering as far as I can tell.

[tmcd35]

Are you looking for virtualisation or clustering?

 

Virtualisation - Running multiple instances of the same OS, or running multiple OS's on a single peace of hardware.

 

Cluster - Running one OS accross multiple hardware boxes

 

I believe Windows Server includes clustering services to load balance work loads between multiple servers.

[Hightower]

Call it what you will. All I know is I've been asked to research this and EduGeek is the place to do it. Surely it still needs some virtualization as there may be 2 OS's spread accross the servers?

[tmcd35]

Start from the begining, what exactly are you trying to achieve? Are you thinking of load balancing workloads, or are you looking for redundancy like vMotion in VMWare were if 1 server dies the OS runs on the other, or are you after something else entirely?

[CyberNerd]

That isn't virtualising, that is clustering as far as I can tell.

 

the virtual machines hosts live in a cluster if you want live migration

[somabc]

I don't understand?

 

How many physical servers do you have and how many OS's do you want to run on them?

[Hightower]

Sorry, my bad.... from the start.

 

Lets say we have 3 physical servers. And we want 2 independant OS's. How do I get both the OS's to work independantly across all 3 servers? Yes, as a way of load balancing but also for redundancy ie we might want to take the 3rd server down for maintenance but nothing is affected as the OS's are still working perfectly across the 2 remaining servers (albeit a bit slower).

[tmcd35]

The best I know of is a VMWare cluster, but it's expensive for so few machines. I believe Xen may also support this (for free?).

 

Basically, with VMWare, you run ESX server on the three servers and run your OS's as Virtual machines. VMWare has a solution called vMotion that live migrates and loadbalances Virtual Machines across availble physical ESX servers.

[CyberNerd]

Sorry, my bad.... from the start.

 

Lets say we have 3 physical servers. And we want 2 independant OS's. How do I get both the OS's to work independantly across all 3 servers? Yes, as a way of load balancing but also for redundancy ie we might want to take the 3rd server down for maintenance but nothing is affected as the OS's are still working perfectly across the 2 remaining servers (albeit a bit slower).

 

The link I posted is a walkthrough to do all those things except automatic load balancing.

Its free if you use Centos.

[Hightower]

Or, is it possible to do it with Windows clustering perhaps, then add some VM's?

[powdarrmonkey]

Xen will do it, but only with a SAN and I think an Enterprise license. VMware will do it but I don't know anything about it.

 

For three physicals and two virtuals, it's going to be hideously expensive though, the SAN alone will set you back something in the region of £10k.

[Hightower]

No problem about the cost - just need a few solutions.

[tmcd35]

Linux.com :: Live migration of Xen domains

 

Xen is the cheaper alternative. And will do the job. Both Xen and vMWare require a 'common data source' or basically a shard hard drive that all three physical machines have access to. vMWare will do this from a NFS share, but ideally a SAN is required for either solution. It's not worth is unless we are talking running atleast 10 OS's across the 3 servers.

[Hightower]

How about running a 4th older server with plenty of storage as the common data source? Will this do?

[CyberNerd]

Xen is the cheaper alternative. And will do the job. Both Xen and vMWare require a 'common data source' or basically a shard hard drive that all three physical machines have access to. vMWare will do this from a NFS share, but ideally a SAN is required for either solution. It's not worth is unless we are talking running atleast 10 OS's across the 3 servers.

 

This has been our strategy. Xen is free and will do what we want. Spend the money on SAN, fibre cards and VT capable servers.

[CyberNerd]

How about running a 4th older server with plenty of storage as the common data source? Will this do?

 

not if you want any sensible performance. you could set it up as an iscsi target though.

[Hightower]

Do you already run a system similar to this CyberNerd? If so, what is your set up?

[richardp]

I used to do this where I worked before in industry. We had a VAX cluster running OpenVMS for our manufacturing and financial system. What you might want to consider is that although the OS will continue to work fine if you down one of the servers for maintenance, you have to remember that any hardware resource within or directly attached to that server will no longer be available. So on a basic level the hard drive in the downed server will no longer be available and therefore none of the data etc... stored on it.

 

We used a stand alone disk array for data storage which meant that if one of the servers failed etc... the other server could continue without any problems and the users would be unaware of any change as all data was still there.

 

The costs as mentioned above are higher as well as making setup and maintenance that bit more complex.

 

Richard

[CyberNerd]

Do you already run a system similar to this CyberNerd? If so, what is your set up?

 

it's not setup. We have an 18month strategy, this summer we put in a SAN. now I'm playing the clustering and XEN

[Hightower]

What are you using (which OS) to run Xen on? I'm having a look at opensuse now.

 

Think the best thing I can do it get three similar spec'd machines and try it, using 2 as the VM servers and one as the central storage.

 

This thing is giving me a headache but I'm loving it as well - it's making my brain work hehe.

 

On a sub-topic, anyone know of any virtualization courses I can go on?

[dhicks]

Lets say we have 3 physical servers. And we want 2 independant OS's. How do I get both the OS's to work independantly across all 3 servers? Yes, as a way of load balancing but also for redundancy ie we might want to take the 3rd server down for maintenance but nothing is affected as the OS's are still working perfectly across the 2 remaining servers (albeit a bit slower).

 

You don't run an unmodified OS across two physical machines, the communications overhead is too much. You need an OS on each machine that supports clustering (various variants of Windows / Linux / etc) and application support for clustering too. I think instead you're maybe thinking of "cloud" computing, where you have a bunch of virtual machines that can be moved around your pool of physical machines at will. I've set our machines up using Xen, which proved to be dead easy with CentOS (like, select "virtualisation" and "clustering" from the install menu, done). I do auto fail-over with DRBD, mirroring whole Linux block devices on physically separate machines, but I know other people prefer to use a SAN (but I figure the SAN is just as likely to fail as one of the processing machines...).

 

--

David Hicks