Virtualisation Questions

tntcoder

tntcoder

tntcoder

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Hi,

I have recently heard a lot of talk about virtualization, the other day someone was telling me how their company had got a new uber intel xeon quad... setup, and were planning on using it as a 'xen box' to isolate different server roles.

Am i correct in thinking this is basically the idea of having 1 host OS, then installing x number of different VM guest OSs for every role you wish to isolate? i.e having like mail server and a web server on separate guests?

I guess this has a lot of positives: Security - cant hack from the guest OS to the host OS, and if something goes wrong for a certain service, you can simply restore a snapshot. But on the downsides does running say 4-5 guest OS's on a single physical server have much of a performance impact?

My other question was in terms of the virtual machine software used for this kind of setup, I hear things like VMWare ESX Server, and Xen mentioned a lot? How do these products differ to your average home users VMWare Workstation / Virtualbox?

Thanks,
Jack
 
Performance is great. In fact most times it's even better becuase with things like VMware you can 'shift around' resources. I.e. if the web server is at a low load average but the mail server is getting hit, you can virtually dedicate more CPU resource to the mail server to keep things nice and even.

You can migrate a RUNNING VIRTUAL SERVER from one peice of hardware to another without users even noticing. (it takes about a second)

This gives nice deployment, backup, and redundancy options as you can imagine.

It also allows for a test bed setup. I.e. create a clone of your virtualised network, and then dick around until it breaks or you fix the problem, or you verified that the new piece of software won't break anything. etc.

It's really cool.

We have 2 main servers running AD, DNS etc as a cluster service, and a NAS backup server and a handful of other servers (fax, dhcp, ftp, etc etc) and to get a middle of the road virtual server replacement would cost about 30 grand for about 50 users.

Perhaps worth it if you're starting up or creating a new wing, but just to replace all out perfectly working kit at that price is a bit much for us.


VMware esx is like a really paired down bare bone install to allow the guest os to have most resources. Not tried virtualbox. but it's free?

VMplayer and server are free to use. Workstation still costs, though.

On linux you have much more options, depending on exactly what you want, but I don't think many come as slick as vmware (yes i know it runs on linux, too)
 
Let's ask Mr T about Virtualisation..

http://www.youtube.com/watch?v=tW1S2tsxVHg&eurl=

*ahem*

anyway, yes. You have a VM for each role. Benefits include ability to easily transfer to a nother machine if hardware fails, backups are complete - i.e. the VM snapshot's include everything, not just data, so there's no need to reinstall before restoring, you just load the snapshot on a different host, and of course managing resources, as already mentioned, is a sinch.
 
whitecrook said:
VMware esx is like a really paired down bare bone install to allow the guest os to have most resources.
Click to expand...

Don't forget (or rather, I'm just making clear by expanding your statement that) unlike the other VM products ESX actually runs on the physical hardware, not inside a host OS. It's sort of like a minimalistic Linux install allowing the guests to have full use of the resources available, which a host OS would otherwise impact on. Sorry, just thought that was worth clarifying for the OP :)
 
whitecrook said:
We have 2 main servers running AD, DNS etc as a cluster service, and a NAS backup server and a handful of other servers (fax, dhcp, ftp, etc etc) and to get a middle of the road virtual server replacement would cost about 30 grand for about 50 users.
Click to expand...

Thanks, this puts it in perspective! I had no idea the hardware would come in at that kind of price and i would hope performance wasn't an issue for 30k+ :D

They sound very interesting though, think i will have a play around with some of the software and mock up some kind of system.
 
Yeah, and you really want one of the newer procs that support virtualiastion (which is just about every mid-high proc from intel over the last couple of years) not sure on AMD.
 
AMD's is called AMD-V and has been included on AMD procs since the F stepping Athlon 64s. On Linux, AMD procs with special hardware for virtualization have a svm flag in /proc/cpuinfo. This is usable with any kernel later than 2.6.21. VMWare workstation only supports Intels in this re3gard. Their other products support both IVT and AMD-V.
 
Hmm interesting thanks, could you tell me if an I could run say ESX Server as the host OS, then say run 3 guest OS's on an AMD X2 4400+ CPU (which from your above post i guess has the SVM flag, i don't have it handy to check) with 4gb of ram.

Guest OS 1: Fileserver NFS or Samba
Guest OS 2: Web server
Guest OS 3: Backup system, maybe rsync.

Would that be enough hardware to run that kind of setup acceptably? Im not talking hundreds of clients here or extreme stability, just for home use and learning :)

Also, maybe a stupid question but is a monitor required to administer ESX Server? Can i do it all over SSH?
 
We're in the process of implementing Xen for a customer, but it's worth bearing in mind that to get the performance they want we're using 4 servers each with 8x 3Ghz cores and 32GB of RAM with an iSCSI SAN for the back end. That's just a proof of concept for the development servers as well and it'll be costing in excess of 100k.

Virtualisation is done best across large numbers of servers and using high end hardware. For a small company the license cost and hardware requirements make it cheaper to keep running 4 or 5 single servers.

Also, the difference (in features and performance) between the free vmware and esx is huge. I wouldn't touch the free versions for production but esx is fine (xen enterprise is much the same).

There's also a few apps that will never virtualise well, Exchange is one of them, heavily loaded SQL servers are another.
 
How easy would it be to do something like this in virtualbox? I want to have a MS access server and windows filesharing, I'm only running around 5 clients, so it won't be a massive load. I was going to use ubuntu as my host OS.
 
I just bought VI3 for a client and I think it cos just less than a grand for each host license (don't know, I'm not in procurement!). So it's not really for home use. Also, you'll get very mixed results running on desktop hardware as it's only tested to run on certain server boxes (although I know it runs on things other than what's on the ESX HCL - but you won't get support for this).
 
MikeHunt79 said:
How easy would it be to do something like this in virtualbox? I want to have a MS access server and windows filesharing, I'm only running around 5 clients, so it won't be a massive load. I was going to use ubuntu as my host OS.
Click to expand...

For home use Virtualbox is fine, for anything else I wouldn't recommend it.

For five clients its hardly worth virtualizing tbh as all those services would happily run on one system.
 
tntcoder said:
Thanks, this puts it in perspective! I had no idea the hardware would come in at that kind of price and i would hope performance wasn't an issue for 30k+ :D

They sound very interesting though, think i will have a play around with some of the software and mock up some kind of system.
Click to expand...

As some people have said above, ESX is really an enterprise solution. To see a farm of 30 hosts running about 800 (or more) servers with HA and DRS (where guests are shifted on the fly between servers due to heavy load on the current host) really is a fantastic thing! However, one of the requirements for these is shared storage. At the very minimum, a shared SCSI bus, however to get the best of this, a good SAN is needed. It really does depend on what you need it for and how much you're willing to pay. A lot of companies will say "I want the best" and when they find out just how much the best costs, they quickly re-evaluate their thinking...

bigredshark said:
Also, the difference (in features and performance) between the free vmware and esx is huge. I wouldn't touch the free versions for production but esx is fine (xen enterprise is much the same).
Click to expand...

I disagree - VMWare Server (previously GSX) is distributed for free, even to an enterprise environment - but as you say, there are MASSIVE feature an performance differences. It entirely depends on what you need from it: if it's consolidation of low load servers and redundancy isn't a huge issue, then you really can't lose with the price... however, if you need things like vmotion, ha (continuous HA is scheduled for the next release of ESX, btw) or drs - then ESX is the bad boy for you.

As for the smaller businesses, it's probably better consolidating low load servers using VMWare server on a base linux install (i.e. not a bloated distro like Ubuntu or OpenSuSE).
 
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.walls said:
As for the smaller businesses, it's probably better consolidating low load servers using VMWare server on a base linux install (i.e. not a bloated distro like Ubuntu or OpenSuSE).
Click to expand...

Possibly, but with real server hardware available from the big name vendors for less than £500 these days I'd be tempted to buy individual boxes...
 
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