Thin Client and Virtual Machines Thread, What servers would be candidates for virtualisation? What do you have virtualised? in Technical; We currently have 20 servers and I've been learning about HYPERV recently.
I was wondering what servers would be good ...
30th April 2011, 02:05 PM #1
What servers would be candidates for virtualisation? What do you have virtualised?
We currently have 20 servers and I've been learning about HYPERV recently.
I was wondering what servers would be good candidates for virtualisation.
I'm guessing things like Exchange \ MSSQL \ SIMS \ DCs shouldn't be virtualised as they use too many resources.
I assume things like DNS \ DHCP \ Print Services \ RO-DCs would be good suggestions (obviously having a non Virtualised server with DNS \ DHCP on as well for redundency).
So do these look ok? What else would you virtualise and what servers would you avoid being virtualised?
I suppose the best way is to see what other people have done and here from their experiences regarding what works and what doesn't.
30th April 2011, 02:25 PM #2
To be honest pretty much everything can be virtualised if you can allocate appropriate resources to it. I've virtualised, SQL/Exchange/Sharepoint/SCCM/SCOM/DCs/SIMS/DNS/DHCP/Print Servers/File servers etc all without a problem. You just need to make sure that each has adequate vCPU(s)(remembering that 2+ vCPUs isn't always better than 1 vCPU!) and an adequate amount of RAM. One thing that's also normally overlooked (and results in poor VM performance) is making sure that your disks (whether thats a NAS/SAN array or local disk) is up to handling the IOPs and throughput you need for the number of VMs your going to be running.
I like to keep one physical DC (with DNS) so you don't have everything in one basket, but other than that I don't tend to run physical servers any longer. The benefits of a virtualised system (better resource utilisation, improved DR/HA, easier to backup etc) outweigh any small loss in performance you may find, and to be honest I haven't seen any loss in performance in the virtualised systems that I'm running.
30th April 2011, 02:27 PM #3
To be honest I have Virtualised Everything as long as the Servers you use are of Good Spec to do what you need to be honest it doesn't seem to be a big problem and you allocate resources Processors, RAM, Disk space, Seperate Network Card where needed correctly it shouldn't be a problem.
I have virtualised MSSQL\SIMS\DCs and DNS\DHCP I have two DC's two Running DHCP\DNS etc I also have one Physical box that isn't virtualised as per Microsoft recomendations but to be honest use this for running managing Backups etc and is handy if you do have an isue with your virtualised setup as you still have a route.
We are using Citrix Xenserver for Virtualisation.
I have run this setup up at a couple of places and doesn't seem to have a big issue.
30th April 2011, 03:41 PM #4
As mentioned above, almost everything can be virtualized as long as the hardware is sized appropriately to handle the workload. Like Soulfish, we have virtualized everything except for a single physical DC. One thing to be aware of though is that you should not use Hyper-V's dynamic memory feature on your Exchange servers. Doing so can result in performance issues.
SQL Server on the other hand is fine, but make sure you read the following links because there are a few caveats.
Many of the performance improvements in recent versions of Exchange are based on the efficient use of an appropriately-sized RAM allocation. This is particularly true of improvements that are related to reductions in I/O operations. The performance optimizations rely on Exchange caching data in RAM. When RAM is dynamically reduced, the expected performance of the system cannot be achieved. In this scenario, Exchange may exhibit reduced performance, or end-users may experience reduced performance when connecting to Exchange. Therefore, for virtual machines that are running Exchange in a production environment, it is best to turn off memory oversubscription or dynamic memory allocation.
Instead, configure a static memory size that is based on the appropriate values for Exchange 2007. (Source
SQL 2005 and later Enterprise and Datacenter editions are required to take advantage of Dynamic Memory in SQL VMs. This is because the lower editions (Express, Standard, Web and Workgroup) donít support hot-add memory, something that was the domain of high end hardware prior to Dynamic Memory.
SQL vNext (codename Denali) is probably going to allow the Standard edition to support Dynamic Memory. (Source
30th April 2011, 03:50 PM #5
We currently have 9 servers virtualised using XenServer on two seperate hosts, all with local storage. I've got an ageing SIMS server and the main DC which is coming to the end of its warranty so will be buying a beefy server this year to move these onto the one physical box. For some reason, I just feel happier leaving Exchange on a physical machine (don't know why!). But, as said, no reason why everything can't be virtualised.
30th April 2011, 06:25 PM #6
We've almost moved to a compleatly virtulised enviroment here on HP DL165G7s (AMD 8 core processors) with Hyper-V and Server 2008R2 Datacentre - going to be getting a HP MSA as soon as the money (magicly) appears for it so we can move our aging storage server onto Hyper-V as well.
Again as people have said before make sure you get the right number of disks - a large number of smaller capacity disks (say 72Gb or 146Gb 10 or 15k) for your server OSes/Databases will go a lot better than 500Gb 7.2k drives (which are better suited to data storage).
30th April 2011, 06:33 PM #7
Something to watch out for. Do not use snapshots on DC's. If you restore a DC from a snapshot you can cause a role back and this can cause major problems with AD.
30th April 2011, 11:22 PM #8
That depends which resources you mean - CPU, RAM or disk. Your chosen virtualisation system should, hopefully, introduce minimal performance/size overheads for each of those. If you're worried about disk performance (for database-driven applications such as those you list above), simply assign your database VM a whole, raw block device instead of a virtual disk file - just give it a RAID array and leave it to organise data as it sees fit.
Originally Posted by Sam_Brown
As pointed out above, DCs work just fine as VMs, just don't snapshot them - use DC replication to backup and mirror DCs.
If you're using remote (e.g. iSCISI) or mirrored (e.g. DRBD) storage, it might be a good idea to assign your print server a decent-sized scratch area as plain, local storage to save on network traffic and delay - it doesn't matter about print jobs being saved in an outage, after all.
I assume things like DNS \ DHCP \ Print Services \ RO-DCs would be good suggestions
Remote Desktop Services - treat those as client machines, with a restore image handy to re-image if neccesary. Someone did have a requirement to use older 32-bit Terminal Services, limited to 4GB of RAM, on a newer 64-bit server with 24GB of RAM and so split the server up in to several virtual servers, but if you're starting from scratch you should just use 64 bit Remote Desktop Services anyway.
what servers would you avoid being virtualised?
3rd May 2011, 02:05 PM #9
Would echo the comments here, almost everything can be virtualised, given the right setup and tuning, we have some customers with VM's running 64GB of RAM using appropriate disk configurations that show equal SQL performance as their physical counterparts, even with the hypervisor overhead. The key is to get your tuning right, as Soulfish rightly points out configuring the VM's right in the first place is the key as with all hypervisors there are limits to how virtual symmetric multiprocessing works so that indeed 1vCPU can sometimes yield quicker results than 4vCPUs on contended hosts.
The first thing to do is to select the best possible hypervisor for your needs, lots of people opt for hyper-v as they see it as an easy migration path from physical windows, when I would place it third in my top three hypervisors after ESXi and XenServer, it is right for some use cases, but for most I would go with another offering.
The second thing to do is size your target environment based on your current workloads, this can be a simple paper exercise sizing the Virtual Machines based on their current use to a proper survey with Capacity Planner or a third party tool.
The third thing to do is to pick your storage and backup strategy, will you go for shared storage, use an existing SAN, pick some cheap iSCSI offerings or just use local disks. Will you leverage hypervisor-aware backups or carry on with your existing agent based backups.
It can be as simple or as complex as you need it to be, if you need any help or specific advice, drop me a PM
and Good Luck!
3rd May 2011, 02:45 PM #10
- Rep Power
Sorry to hijack this thread but I'm in the process of suggesting to the powers that be update some of our servers, and therefore was looking at virtualising our servers. At the moment, all our servers are physical apart from one (BlackBerry server).
Some of them are quite old, and I thought of pricing up one or two beefy servers, virtualising them such as the mail server, apps server, file server and print server. I will probably leave both DC's as they are. If you were in my case, which servers would you recommend?
One of my main future projects is to invest in new kit so any advice would be greatly beneficial as I could bring reasons why to the meeting if this ever happens?
3rd May 2011, 02:48 PM #11
Virtualize everything, then enjoy! I did, it's reduced my workload and stress 100%! I've gone from 16 servers to 2 hosts and a 1 SAN...and 2 additional switches and soo many NICS!
3rd May 2011, 03:32 PM #12
Originally Posted by mo_vigilante
HP do a dual proc server at a very good price point in the shape of the ML150G6 server, its a quality piece of kit considering it's place in the market and if configured right make perfect entry-level virtual hosts. Most of the schools and colleges we work with buy them, if not there are some decent Dell offerings, but no dual-processor models that come in at this price-point.
Drop me a PM if you need any further info and I will send you a copy of our standard Specification that has all the options on the VMware Hardware Compatibility List - which means it will likely work with Citrix and MS as they are much more flexible in terms of supported hardware config.
3rd May 2011, 03:36 PM #13
I've mostly used Dells in the past - we currently have a couple of Dell R510 servers with (I think) dual quad-core processors, 32GB of RAM and 8 harddrive slots apiece. That seems like a pretty cost-effective option for most schools - Dell do quad-processor machines, but those start off at £3,000 or so. There's no need to buy a separate storage server, you can simply mirror disk volumes between the two servers. You'll probably find that your older machines can have some more harddrives crammed in to them somewhere and be used as backup storage.
Originally Posted by mo_vigilante
3rd May 2011, 03:52 PM #14
We putting all of ours onto a VMWare infrastructure over the next few months, going for 3 hosts to ensure we have a bit of breathing space should one fail and an iSCSI SAN.
The thing to watch out for is disk IO, if you can try and get capacity planning done beforehand or measure the IO stats with Performance Monitor to give you an idea of what hammers the disks on your physical servers. For us it's our main file server and Exchange 2007 box (definitely worth going to 2010 if you virtualise as the new version cuts IO down by around 70% according to what Microsoft are saying)
3rd May 2011, 05:47 PM #15
- Rep Power
Originally Posted by andrew-virtusolve
Thanks for that info - I've sent you a PM when you can get chance to read.
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