curiousagain
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Contributor

Number of VM's per Host

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Hi,

I have a very powerful HP server with 64 GB RAM & 2 Xeon Quad cores CPUs (8 cores in total).

I'm raising a virtual server in my company to hold other servers which will use my customers.

Each customer will get a server with 1GB Ram & 2 cores and will host ERP software, MS Office and some other software's. This server will use around 10 Terminal server clients.

I would like to know if my powerful server will be able to handle so many servers (60 servers) or you see here any kind of bottleneck.

I read VMware Maximums document, but I need a practical answer.

Thanks.

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Troy_Clavell
Immortal
Immortal

we get about 8.5 VM's per Core in one of our VDI environments, but that running on a 16 core HOST. On our 8 Core boxes we are getting around 6.5 VMs per Core, but can go more.

our first VDI environment we have XP guests with 1GB RAM, 1vCPU (VMware VDM)

our second VDI environment we have XP guests with 640MB RAM, 1vCPU (VMware View using linked clones)

View solution in original post

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JoJoGabor
Expert
Expert

I wouldnt expect to get more than 20 VMs on that host. THe contention is more likely to be memory bus or Disk/IO. Ideally get a capacity plan run on your VMs such as Platespin Recon or VMware Capapcity Planner, this will give you a good idea of consolidation ratio you can expect by monitoring your existing servers.

Also Note that you will get better performance by configuring as many VMs as possible with a single vCPU to prevent VMs waiting for simulataneous CPUs to become available. Onlyincrease to 2 or even 4 if the application is really suffering.

Troy_Clavell
Immortal
Immortal

anywhere from 4 - 8 VM's per core depending on load.

You need redundancy. My advise would be to get vCenter and atleast 1 other ESX Host with the same configuration and set up an HA/DRS Cluster with shared storage.

curiousagain
Contributor
Contributor

Thanks for the useful information,

How can I improve the system that will support ~60 servers? is it possible to improve Memory Bus?

I'm using a SAN, so Disk I/O will be better if I increase the amount of disk, right?

Is there a way to use this tool for free (VMware Capacity Planner)?

BTW: I forgot to mention that I have 2 servers (with the same configuration) which have the HA mechanism between them and a SAN.

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Troy_Clavell
Immortal
Immortal

having another ESX to help balance out the load will definitely help. A 30:1 ratio is much much better.

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curiousagain
Contributor
Contributor

so it's better to put 30 vm on server1 and 30 vm on server2 for a general work and to put HA between them, and if one of the server fails the HA will move all the vm to one server, right?

if yes, will the server be able to run 60 VM?

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Troy_Clavell
Immortal
Immortal

so it's better to put 30 vm on server1 and 30 vm on server2 for a general work and to put HA between them, and if one of the server fails the HA will move all the vm to one server, right?

correct. ( I would also enable DRS to fully automated so the VM's are balanced as best as possible between the two ESX Hosts

if yes, will the server be able to run 60 VM?

yes, but there may be some resource contention. Just ensure your vSwitch that holds your VMs (Virtual Machine Port Group) is configured with atleast 120 ports to support the possibility of hosting all 60 VM's in the event of a host failure.

Ideally if budget allows a 3 host cluster would be ideal

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mehul96
Enthusiast
Enthusiast

It really depends on what runs on these VMs, what you really need is an estimate of the peak and average CPU, Memory, I/O and Network usage for each VM and then apply a factor of overcommitment. In our environment, we try and stick to 20 VMs with 25% over commitment and that has worked well so far. In your case, clustering 2 or more ESX to host 60 VMs and then let DRS handle the load balance and HA take care of failures should work. Obviously, the user experience in case of failure (i.e. 60 VMs on 1 ESX) will not be as good as 30 on 1, so you need to set user expectations accordingly

Mehul

PS: if you find responses helpful, please consider awarding points!

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curiousagain
Contributor
Contributor

Thanks again,

do you know if there is a free tool to estimate how much vm my server can hold (like the VMware Capacity Planner)?

thanks,

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mehul96
Enthusiast
Enthusiast

Not as powerful as the capacity planner but you could use guided

consolidation with converter (if your VMs are windows)

Mehul

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JoJoGabor
Expert
Expert

Yeah the consolidation planner is the only free tool I know of that comes with Vcenter (I think its only available when in Eval mode)

Otherwise VMware Cap Plan you have to do a c2 day course to get hold of - a VAC can do this for you, sometimes free of charge.

Otherwise I would recommend using Platespin Recon, but again you will get most value out of this with a consultant as the results can be spurious.

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VforVirtualizat
Contributor
Contributor

Can you post the model of your server or the speed/series xeons your using?

Also what will you be using for your guest operating systems? XP, Vista, Server 200x?

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curiousagain
Contributor
Contributor

I have 2 HP G6 servers with 64 GB RAM & 2 Xeon Quad cores CPUs (8 cores in total) and a HP SAN

Each VM will have 1GB Ram & 1 core and will host ERP software, MS Office and some other small software's. each VM server will use around 10 Terminal server clients.

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JoJoGabor
Expert
Expert

You may get up to around the 50 or 60 mark in a VDI solution.

Troy - have you managed to get up to 8 servers per core in a 8 core box? What kind of spec VMs were you running? I've generally not managed to get above 30

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Troy_Clavell
Immortal
Immortal

we get about 8.5 VM's per Core in one of our VDI environments, but that running on a 16 core HOST. On our 8 Core boxes we are getting around 6.5 VMs per Core, but can go more.

our first VDI environment we have XP guests with 1GB RAM, 1vCPU (VMware VDM)

our second VDI environment we have XP guests with 640MB RAM, 1vCPU (VMware View using linked clones)

View solution in original post

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curiousagain
Contributor
Contributor

Thanks JojoGabor,

I wonder how the limitation is standing on 8 VM's per core and it's hard to reach even close to this configuration.

How come you didn't succeed to manage more then 30?

do you load your VM's?

My VM's will use minor businesses (word, small ERP etc...), can I reach the limit of 8 VM's per core?

Thanks.

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curiousagain
Contributor
Contributor

Thanks JojoGabor,

I wonder how the limitation is standing on 8 VM's per core and it's hard to reach even close to this configuration.

How come you didn't succeed to manage more then 30?

do you load your VM's?

My VM's will use minor businesses (word, small ERP etc...), can I reach the limit of 8 VM's per core?

Thanks.

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JoJoGabor
Expert
Expert

Initially I thought you were talking about server virtualisation, hence the lower figure. WHen I do capacity plans, setting thresholds of 80% CPU and 90% RAM, they usually come up with a consolidation ratio of no more than 15. Servers tend to average around 5% CPU utilisation. In reality we can usually get these up to 20ish as the tool is quite conservative.

Now for Virtual desktops most desktops average around 1% CPU utilisation and lower RAM utilisation so you can get more per host. Depending on the utilisation you will be able to get many more per host. Also remember that you can overcommit the memory on ESX (fine for a VDI solution, I wouldnt deliberately do it in a server environment) So you may run 50 VMs and give them 1.5 - 2GB RAM each on your 64GB host, as long as the total used memory doesnt exceed 64GB your perfromance will be good.

Sorry for the confusion between server and desktop

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curiousagain
Contributor
Contributor

Thanks JojoGabor,

I wonder how the limitation is standing on 8 VM's per core and it's hard to reach even close to this configuration.

How come you didn't succeed to manage more then 30?

do you load your VM's?

My VM's will use minor businesses (word, small ERP etc...), can I reach the limit of 8 VM's per core?

Thanks.

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curiousagain
Contributor
Contributor

Thanks a lot, you have helped me to understand several things in such environment.

thanks..

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