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Wavefox
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VMware Workstation Maximum VM limit?

Hi all,

I'm running a Dual Quad-Core Xeon system (at 1.6ghz) with 16GB ram. Host OS: 64bit Vista Business.

After getting 24 VMs up and running concurrently (running XP SP2 with 160MB ram per VM), the system was using about 7.25gb of the 16GB ram. I continued to clone more VMs, and when I created the 28th VM, Workstation popped up an error box saying "Maximum number of VMs reached" or something very close to that.

I've done my dutiful Googling, as well as searching these forums, and have been unable to find a reason why this is happening.

The machine has plenty of power to continue opening more VMs - where is this limit coming from, and is Workstation the wrong product to be using? Would Server be better?

Thanks for your time!

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ksc
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Workstation and Server have the same limitation (Server may be +/- 2 or so, but it's not significant), and the limit comes from the OS itself. ESX is tested to 128, and theoretically goes higher.

It's a technical limitation; as I recall, it has to do with the number of connection sockets / waitable events a certain binary (the UI or authd, I don't recall which) can handle simultaneously - though we enforce the limit elsewhere to get cleaner error messages. The limit is OS-specific, is 27 on Windows and somewhat higher (64, 128 maybe?) on Linux. We're dependent upon a certain type of OS resource that isn't easy to increase. We could be more frugal, or we could multiplex better, but it takes time to re-architect certain communications channels. You MIGHT be able to escape it by using multiple Workstation UI windows; I don't recall where the limit gets enforced.

8-way 16GB hosts like yours just haven't been around long enough for this limit to be reached often. Smiley Happy

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Wavefox
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As an addendum, I was able to add more than 28 VMs to a Team (I have 32 in a team now) but I am unable to power on any more than 24 VMs at a time now.

System resources are still not an issue - the main issue is that there is some sort of hard coded limit in Workstation and I need to know what to do to get around it - do I need to run VMware Server?

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ksc
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Workstation and Server have the same limitation (Server may be +/- 2 or so, but it's not significant), and the limit comes from the OS itself. ESX is tested to 128, and theoretically goes higher.

It's a technical limitation; as I recall, it has to do with the number of connection sockets / waitable events a certain binary (the UI or authd, I don't recall which) can handle simultaneously - though we enforce the limit elsewhere to get cleaner error messages. The limit is OS-specific, is 27 on Windows and somewhat higher (64, 128 maybe?) on Linux. We're dependent upon a certain type of OS resource that isn't easy to increase. We could be more frugal, or we could multiplex better, but it takes time to re-architect certain communications channels. You MIGHT be able to escape it by using multiple Workstation UI windows; I don't recall where the limit gets enforced.

8-way 16GB hosts like yours just haven't been around long enough for this limit to be reached often. Smiley Happy

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Wavefox
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I appreciate the response - so, if I switched to a variation of Linux for the host OS, I'd likely have better luck doing this?

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ksc
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Yes; Linux is tested to 64 VMs, Windows tops out around 27, but should start emitting warnings past 24.

I would suggest trying this on Linux before committing to it; large numbers of VMs on high-end machines are not a common test case, so you might end up tripping over obscure bugs.

(The root cause is that the Windows function MsgWaitForMultipleObjects can only wait on 63 handles, and starts breaking past that. Two handles per VM plus other overheads gives the 27-VM limit.)

MudLevelGnuby
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Might I recomend Red Hat Enterprise Linux.

Its pretty tough, well tested, and somewhat of an industry standard.

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Wavefox
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Okay, I have installed Ubuntu Linux 7.04 (64bit edition to handle the 16GB memory) and got VMware Workstation (Edit: version 6.0 has been used for all of this testing) up and running... and it will not let me run more than 24 VMs at once.

I tried opening up another VMware Workstation window and running more VMs from there as well, and it is not letting me power more on.

What gives? I thought you said I could do up to 64 VMs on Linux?

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Wavefox

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Wavefox
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The Linux version appears to have a 24 running VM limit as well for some reason - is this a bug?

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ksc
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Hmm. The bug fix for obscure errors with high numbers of VMs was to put in a hard limit. Something not noted in the bug, sigh. Apologies for leading you astray.

Server 1.0 has a 64-VM limit (though the windows version tops out at 27). Workstation and Player have a 24-VM limit. I've filed a bug to raise it; there is no reason for the Linux limit to have regressed.