VM Slow Down Problem In HYPER-V

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Hi I have following dedicated server,

Dual Intel Xeon 5639
2.13Ghz - 2 Processors
12 Cores / 24 Threads
24GB DDR3 RAM
2TB SATA|| 7200RPM
1Gb Dedicated Port.
Windows Server 2008 R2 64-Bit Standard Edition.

I have configured HYPER-V on this server. Right now i have added few virtual machine on this HYPER-V server.
Configuration of all VM are as follows.
Windows server 2003 Standard Edition.
512MB Ram

Hyper-V Settings:
Processor
1]No. of logical processor - 1
2]Virtual Machine Reserve(%) - 0
3]% of total system resources - 0
4]Virtual Machine Limit(%)- 100
5]% of total system resources - 4

Using above settings for all VM, I should be able to run around 20 VM on this server without any processor overload problem. But after running more than 11 VM (remaining 9 VM status is off) simultaneously with 60% processor load on each VM. All apps & system resources running slow in each VM. If I am correct i have 12 physical core, this give me 12X8 = 96 virtual processor count on this server. I have given only 1 virtual processor to each VM, total of 11. It should be enough cause each VM never using more than 60% virtual processor load(Also 512MB RAM is never used as full. Around 50% max is used). On Hyper-V Dedicated server nothing is running except Hyper-V. I have restarted my dedicated server each day. But it still shows this problem. I have increase each VM logical processor count from 1 to 2. Still same problem. How can I make correct settings for each VM in my dedicated server HYPER-V, so it can run 20 VM without any issue?

Posted 23-Jan-14 3:49am

Nilesh bhope

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3 solutions

Solution 2

E.F Nijoeber is on the right track...

Windows always keeps some free memory, but in low memory systems it will use the page file much more aggressively. Since the page file is disk based, you are probably having a lot of disk reads/writes.

Because only one application (or VM) can read/write to the disk at one time, you have a resource contention. This will slow things down quite a bit.

If you are wanting to run this many VM's on a single machine, you will need to provide a better disk system than a 2TB 7200 SATA. You will probably need some sort of disk striping system and high performance disks.

Take a look at your physical machine disk IO activity, that should tell the story.

Posted 23-Jan-14 4:15am

Ron Beyer

Solution 4

I agree with Ron : IMHO your problem is not the memory, or the processors, but the disk.

If I get you right, you have a single 2 TB / 7.2K / SATA disk drive?

For an hypervisor running several virtual machines, I recommend :

- a true RAID extension card with its own battery

- at least a RAID 5 array, preferably with SAS disks instead of SATA (10K or 15K, it depends on you/your budget) to store the virtual disks.

There is no magic in that : imagine you have ten virtual machines, each one of them trying to access a single SATA disk at the same time. Your performance issues are not surprising to me.

Hope this helps :) Good luck.

Posted 23-Jan-14 4:59am

phil.o

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Nilesh bhope 24-Jan-14 6:25am

I think in this matter, a 128 or 256 SSD will have better option in place of SAS. I have not checked yet IOPS limit warning. This might be culprit.

phil.o 24-Jan-14 6:31am

IMHO, the price increase in using SSD drives to store .vhd or .vhdx files is not worth the performance gain. SAS drives are really good for that, they have nice random-access performances, and higher capacities than SSD drives.

Nilesh bhope 31-Jan-14 5:26am

I wanted to run around 20VM for above configuration. Each VM will need around 6GB disk space. Right now I thinking for a single 128GB SSD for 10 VM. A mere $25/monthly price is increased. SSD will always beat SAS. Pricing is not issue for me. a 256GB ssd just cost around $60/monthly. That will give me around 20VM performance boost. What do you think for 128GB SSD for above configuration for my server with 10VM?

phil.o 31-Jan-14 6:38am

I can't say ; just be aware that your SSD drive has only a single controller, thus it will not allow several VM's to access it at the very same time.
Sharing the controller's resources between 20 virtual machines seems a little nonsense to me, but I never really tried it.

Nilesh bhope 31-Jan-14 8:01am

Are there any cost effective way to provide high IOPS to each VM? I think RAID setup with 20 hard disk setup is too costly.

phil.o 31-Jan-14 8:18am

I'm afraid there is no magic, no.
If you want high IOs with 20 VMs, then you have to invest some money in it.

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E.F. Nijboer · Accepted Answer · 2014-01-23T04:06:00

I would really try to increase memory available to the VM's. You can use dynamic memory (check links). Even though it looks like memory isn't used, it is keeping some memory free for unpredicted occasions and therefor won't use all of it.

http://www.altaro.com/hyper-v/hyper-v-dynamic-memory-explanation-and-recommendations-2/[^]

http://technet.microsoft.com/en-us/magazine/hh709739.aspx[^]

Good luck!