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Hyper-V server and RAM

Posted on 2011-11-01
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Last Modified: 2012-05-12
I have a Windows Server 2008 R2 Standard box using Hyper-V. The box has 12GB of RAM. It is running 4 VMS which are
File Server 2GB RAM
DC-EX        2GB RAM
Accouting   3GB RAM
EX              2GB RAM

Thats a total of 9 GB of RAM. I am guessing that the reaming 3GB of RAM are being used by the Hyper-V Server? Is there a way to determine that? I right clicked on my computer>properties and it says 12GB which is what the server has installed but doesnt show what the OS is using for itself. The VMs run fast but the Windows Server 2008 R2 Server (with Hyper-V) runs slow. I am going to purchase 32GB of RAM to add to the box. Would that make a difference? Also how do I allocate more RAM space to each VM once I get more RAM.

I know its more then one question but they all go hand and hand with eachother. Thanks for youe help.
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Question by:IT_Fanatic
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by:Neil Russell
ID: 37063378
With Hyper-V, it is infact an APP running under Windows Server 2008 R2 so its memory consumption is from the 12GB that is managed by the server. The VM's wont always be using the ammount of memory allocated to them, thats the beauty of virtualization.
To add more memory to a VM once you have installed more in the physical host just edit the virtual machines settings and up the memory.
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Author Comment

by:IT_Fanatic
ID: 37063396
any reason why the server just runs slow when opening up any program but the VM's are blazing fast? Could the 12GB not be enough or is it something else?
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by:Neil Russell
ID: 37063611
the server should not be running any other applications, it is a virtulization host.
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by:Neil Russell
ID: 37063621
Is EX an exchange box?
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by:kevinhsieh
ID: 37063694
Sounds like a typical disk IO issue. What kind of disks and RAID level are you using? I assume that EX means Exchange. The minimum supported RAM for an Exchange server will all roles is 8 GB. Your DC can go down to 1 GB no problem.

Windows Standard can only go to 32 GB RAM as I recall, so that is the max you can use in the host unless you upgrade to Windows Enterprise or switch to Hyper-V Server. Hyper-V server is free, but it requires a clean install and there is no GUI, so all management is done via Hyper-V manager on a remote server or workstation.

In hyper-V, the RAM is hard allocated to a VM once the VM is turned on, RAM is the one resource that isn't shared. That said, with Hyper-V R2 SP1, there is dynamic memory, which does allow VMs to use the pool of free RAM to go beyond their initial RAM assignment if required, and that RAM can be given back to the pool if other VMs need it more.

Hyper-V needs about 384 MB for the host, plus another several MB per VM. It won't let you start a VM if there isn't enough free RAM for it.
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Author Comment

by:IT_Fanatic
ID: 37063847
The only thing I have running on the hyper-v server is acronis to do my backups and its also a domain controller. So your telling me I cant allocate more RAM to a VM after its setup? I thought you can turn off the VM and allocate more ram and just turn it back on.

Also the server has two RAID 5's and the drives as SAS
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by:Lee W, MVP
ID: 37063932
> With Hyper-V, it is infact an APP running under Windows Server 2008 R2
My interpretation of the above disagrees with this.

Hyper-V drivers and related services load as quickly as possible.  It's no more an app than VMWare ESX is an app running on Linux.  (Virtual Server was more of an app).  Hyper-V (like ESX/ESXi) is a Type 1 hypervisor - a bare metal Hypervisor that runs with Windows as its management interface.

Hyper-V 2008 R2 -- if you've installed Service Pack 1 -- Supports memory overcommit with supported operating systems and OS configurations.  Exchange and I believe SQL are NOT supported configurations.  However, a virtual file server or application server or DC would be.  You would set the minimum and maximum memory and priority of the VM in the Hyper-V manager.  If you're just using Windows as a management platform for Hyper-V then I would suggest you your issues are likely as suggested, as a disk I/O issue.

You should be able to adjust RAM configuration by shutting the VM down.

I agree, the Server 2008 R2 standard edition is limited to 32 GB of RAM.  If you want to use more, You'd likely have to reload Hyper-V 2008 R2 Server (the free version without GUI management) and use that - that supports considerably more RAM (unless you're using Enterprise or Datacenter right now).

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Author Comment

by:IT_Fanatic
ID: 37064089
I do have service pack 1 installed. Disk I/O issues is that hard drives that are going bad?
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by:kevinhsieh
ID: 37064764
It isn't that your hard drives are failing per se, but that they can't deliver enough read IOPS for your environment. Slow disks are usually most noticable when trying to navigate the GUI, clicking on the Start Menu, etc. You should check to make sure that your RAID isn't degraded

Why do you have two RAID 5 arrays? A single RAID array is going to perform better because all drives will be available to all environments, instead of separating everything out to just a few drives each. A single RAID 10 will perform a bit better, and even a single RAID 5 will give you better overall performance.
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Author Comment

by:IT_Fanatic
ID: 37064872
We have 3TB of HDD and Windows Server 2008 only saw a certain amount. Thats why the old IT guy created one raid were the OS and 3 vms reside and raid 2 only has one VM which is exchange. How can I tell if the raid is degraded? I have a dell R510 server.
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by:kevinhsieh
ID: 37064959
Look at the Dell OpenManage software that should be installed.

The old IT guy did a dumb move. The correct thing to do would be to create two logical drives using the RAID controller. One smaller MBR drive for the host OS, and a second larger GPT drive for the VMs. A MBR drive, which is required when booting using traditional BIOS can only be 2 TB.
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Author Comment

by:IT_Fanatic
ID: 37065041
I checked the RAID using Dell OpenManage and I have green check marks down the board. How can I improve conformance then if your saying the RAM is not the issue.
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Author Comment

by:IT_Fanatic
ID: 37066102
Below is the status of my Raid
raid.jpg
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by:kevinhsieh
ID: 37066197
Backup everything. Wipe the RAID and reconfigure as two RAID sets. The first one needs to be maybe 100-200 GB (depending on your backup software needs). The second RAID set should be RAID 10 usinging all remaining space. Configure it as GPT format, and put all of your VMs there.
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Author Comment

by:IT_Fanatic
ID: 37066332
I will be honest with you that is really not an option right now. Is there anything else you can recommend to make the main OS run faster?
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by:kevinhsieh
ID: 37066681
Move a VM to the other RAID array, defragment, be patient, add RAM to your VMs on the first array so they hit the disk less.
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Author Comment

by:IT_Fanatic
ID: 37066702
I have 1vm which is exchange on one raid. The is and 3 other vms on the other raid. I have plenty of HDD space. Would just buying more ram and distributing it to the vms and the rest for the os help?
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by:kevinhsieh
ID: 37066843
Possibly. If you give your VMs more RAM, they can do more caching and hopefully hit the disk less, which will reduce disk contention and hopefully make whatever you are trying to do from the server console seem a little bit more responsive.
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Author Comment

by:IT_Fanatic
ID: 37066860
Wait so your saying the vms take disk space for memory usage as well. If I am understanding that is what your saying by disk less
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kevinhsieh earned 2000 total points
ID: 37067119
Well, that is true, but now what I am saying.

Any Windows machine, physical or virtual, will use both disk and RAM for operations. The more modern versions, Windows Vista/2008 and above can use huge amounts of RAM to cache information that they would otherwise need to read from disk. The more RAM they have, the more they can keep data in RAM instead of having to read and write it to disk. Disk is the slowest part of the computer, and the reason why adding more RAM to a system will make it run better, up to a point. Having too little RAM will cause the system to have to contantly use virtual memory, which will cause the machine to slow down to a crawl. Since your disks are shared between several systems, anything that slows down your disks will slow down all systems. My thinking is that if you add RAM to the VMs, that will reduce the amount of disk activity that the VM generates, will will leave more disk IO available to the other machines, including the host.
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by:kevinhsieh
ID: 37067124
Sorry, should have been "Well, that is true, but not what I am saying." in regards to VMs taking disk space for memory usage.
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Author Comment

by:IT_Fanatic
ID: 37067909
Thanks for the advice. I'll let you know how it goes when i add more RAM
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by:James Haywood
ID: 37071401
Hyper-V is not designed to be used in conjunction with other roles. You would be much better off transferring the DC role to a VM (even if just using 1GB RAM). That would make a huge difference to the host performance.

Once you are using the physical server for running VMs only then you will rarely need to logon anyway therefore removing the problem you are encountering.
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Author Closing Comment

by:IT_Fanatic
ID: 37072992
Once I add more RAM ill let you know how it goes
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