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Overhead with Hyper-V

Posted on 2014-03-03
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Last Modified: 2014-11-12
Hi,

  I am working on new server project and trying to determine if I should go with Enterprise SATA HDs 7200rpm or SAS 15K HDs. Here is why I am in a quandry.
  A year ago I installed a new server w/ 32GB and 2 x 2TB Enterprise SATA HDs doing RAID 1. I setup W2012 to run Hyper-V (200GB HD space and 2GB RAM). On the top of that, I created three VMs: (1) SBS2011 with 16GB RAM, 200GB OS partition, 800GB Data partition)  (2) Windows 2008 R2 Terminal Server with 6GB RAM, 200GB HD  (3) Another Windows 2008 for Quickbooks Database server with 4GB RAM, 100GB HD

  Whenever I connect to this server whether I am connecting to Hyper-V or any of the VMs, I just feel that the respond is much slower than my (1) 5 years old "Dedicated" Windwos 2003 SBS Server with 4GB RAM, LSI HW  RAID Controller w/  Enterprise 7200rpm 1TB HD x 2 (RAID 1).  or (2) 2 years old VMWare box that has 10 VMs w/ 32GB RAM and six 600GB SAS 15K on RAID 10.

  Having said that, is slowness that I am experiencing normal given the fact that it has Hyper-V with VMs on 7200rpm HDs? too much overhead?

  So I wonder if I should just setup this new server, w/o HyperV, as "Dedicated" SBS2011 only with 16GB RAM and setup another server box with HyperV to run a couple of VMs such as Terminal Server or what not. I was trying to save a few dollars by running EVERYTHING (OS + VMs) on an economical 7200RPM SATA HDs. As long as it has lots of RAM, I thought it would be ok.
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Question by:sglee
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Cliff Galiher earned 38 total points
ID: 39901289
Comparing 2 7.2k sata drives to 6 15k sas drives is like comparing a Formula 1 racecar to a scooter. You will notice a performance difference, even with tons of RAM. There is a reason consumer SSD droves are increasing in popularity despite the cost. I/O speed matters.

Now with that said, don't use SBS 2003 as some sort of benchmark for SBS 2011, no matter which disks you choose. They are products from a different era and there are so many things going on, I couldn't cover them all. Just accept that pound for pound, SBS 2011 is more full featured, more secure, more supportable... and slower.

Hyper-V overhead is minimal.
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Assisted Solution

by:Lee W, MVP
Lee W, MVP earned 38 total points
ID: 39901299
I would definitely be looking at the disk subsystem.  RAID 5 takes a hit on writes but reads are MUCH faster than RAID 1 and you're doing more reading than writing in most cases.

Further, what kind of disks did you create?  Fixed VHDs or Dynamic VHDs?  If the latter, did you create partitions on the physical drive so the dynamic VHDs wouldn't fragment?

Your old server has 3 potential issues I'll point to:
1. 7200 RPM drives (slow to begin with) in a RAID 1
2. 3 VMs running on said drives splitting the reads and writes across only 2 drive heads (1 when writing)
3. Potential for fragmented VHDs (depending on configuration).

And please don't compare a VMWare box with 6xSAS 15 in a RAID 10 to a Hyper-V box with a single mirror of 7200 RPM drives.  That's like complaining your school bus (2x7200 RPM RAID 1) doesn't accelerate as fast as your Ferrari (6x15K RAID 10).
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by:Philip Elder
Philip Elder earned 149 total points
ID: 39901304
RAID 1 is a bad idea for SBS whether on bare metal or hypervisor as a VM.

SATA is a bad idea on servers. Period.

Our base configuration for any hypervisor deployment would be hardware RAID, 512MB cache minimum backed up either by battery or non-volatile flash RAM, (6) 10K 2.5" SAS spindles, and RAID 6. If the box can handle 8 drives then we size down and load up (8 drives total).

Back up the VMs, set up your newly installed SAS disks, set a logical disk of 90GB for the host OS and the balance of space available to a second logical disk both done in the RAID BIOS.

Configure fixed VHDX files for your various VMs (SBS_D0, SBS_D1, RDS_D0, RDS_D1, ETC) prior to creating the VMs in Hyper-V Management.

Once the VMs are set up restore your backed up VMs to the newly configured VMs. You will need to clean up NICs and run the Fix My Network Wizard in SBS after setting the correct static IP.

This is the method we would use to make these kinds of changes on the host.

Philip
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Author Comment

by:sglee
ID: 39901317
@Lee W, MVP
That's like complaining your school bus (2x7200 RPM RAID 1) doesn't accelerate as fast as your Ferrari (6x15K RAID 10)  .... Lol.
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Author Comment

by:sglee
ID: 39901516
@Lee
VM SettingsDisk ConfigurationI used VHDX on all three VMs in Hyper-V Server.
"did you create partitions on the physical drive so the dynamic VHDs wouldn't fragment?" ---> I don't know how to answer that. Please see the screenshot of CompMgmt.
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Assisted Solution

by:David Johnson, CD, MVP
David Johnson, CD, MVP earned 38 total points
ID: 39901988
having the paging file on the same spindle as the operating system will make things slower
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Assisted Solution

by:Philip Elder
Philip Elder earned 149 total points
ID: 39902012
We set a static page file of 4096 MB (4GB) by default so no fragmentation will be had.

If the host is swapping in and out there is a bigger problem going on as we have not seen that behaviour to date.

Philip
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Author Comment

by:sglee
ID: 39902190
Phil
If the RAM allocated for Sbs2011 is 16GB, then isn't 4GB for paging file too small?
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LVL 38

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by:Philip Elder
Philip Elder earned 149 total points
ID: 39902460
The paging file for the host is set to 4GB.

We don't touch the guest page file setup as the VHDX files span multiple spindle sets as a rule other than perhaps setting it to a static size. Paging in today's OS and server apps is essentially performance death.

Philip
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Assisted Solution

by:Cris Hanna
Cris Hanna earned 37 total points
ID: 39902982
I absolutely agree with other comments regarding the disk performance and going with SAS drives.  But I'm surprised that no one has commented about the amount of Ram allocated for SBS.  16gb is really a minimal amount for SBS.  So perhaps you should consider that the host OS for Hyper V should be Datacenter so you can have more than 32gb of Ram.
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Author Comment

by:sglee
ID: 39903065
VHD Option Screen@Philip
"Configure fixed VHDX files for your various VMs " ---> So setting it "Dynamic" is a bad idea?
How do you create fixed VHD and say you set the size to 500GB, but need to expand later. Then what do you do?
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Assisted Solution

by:Philip Elder
Philip Elder earned 149 total points
ID: 39903277
Hyper-V Management --> New --> Virtual Hard Disk --> VHDX --> Fixed --> xxxGB.

We allocate accordingly. We tend to leave about 15% to 20% free for NTFS performance purposes but that's it. Disk size in the RAID array would be such that the current data set plus three years anticipated growth at the minimum.

Yes, Dynamic is a bad idea. If one allocates more space to the dynamically expanding VHDX files than is available on that server physically Hyper-V will put the VMs into a Paused Critical state as there would be no more room to grow.

Plus, over time the dynamically expanding files get fragmented thus causing performance loss. This is not so important where there are 16 or more spindles in a SAN/DAS/JBOD setting but is important for our smaller spindle sets.

Philip
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Author Comment

by:sglee
ID: 39903291
Philip,

 How can I change to "Fixed" from Dynamic on "dynamic" on existing VMs?
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Expert Comment

by:Philip Elder
ID: 39903340
With the VMs off use Edit Disk in Hyper-V Management.

Edit Disk
Note the conversion process requires disk space to complete.

Another option is to back up, recreate new fixed VHDX files, and restore.

Philip
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Author Comment

by:sglee
ID: 39903350
Which option to choose:  Compact or Convert?
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Expert Comment

by:Philip Elder
ID: 39903441
Convert.

Philip
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