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VMWare Server (free version)

ebaycj

ebaycj

Diamond Member
First off, I'm planning to run either Ubuntu 6.06 or 2003 Server x64 as host OS.
Athlon 64 X2, 4GB DDR2, 2x400GB NVRAID (RAID 1).


Obviously I will have to allocate at least 256mb for the Host OS's purposes.

My question is: Besides the host OS memory (256mb), out of the remaining 3.75GB how much will be available for VM's ??

I know that windows does 2GB/2GB or 1GB/3GB (with /3gb boot switch) splitting for kernel memory vs program memory, I assume Linux has a similar requirement. Does this affect VMWare Server at all?



Thanks for any clarification

 
Everything you've asked is irrelevant in the 64bit environment. You could allocate all 3.75GB to one VM if you wanted to.
 
Memory Use on the Host
Host operating systems do not behave well when they run low on free memory for their own use. When a Windows or Linux host operating system does not have enough RAM for its own use, it thrashes ? constantly swaps parts of itself between RAM and its paging file on disk. To help guard against virtual machines causing the host to thrash, VMware Server enforces a limit on the total amount of RAM that can be consumed by virtual machines.

In general, the sum of the memories of all currently running virtual machines plus overhead for the VMware Server processes cannot exceed the amount of physical memory on the host minus some memory that must be kept available for the host. You can adjust the amount of virtual machine memory that the host operating system can swap to disk. For more information, see Using Additional Memory.

Some memory must be kept available on the host to ensure the host is able to operate properly while virtual machines are running. The amount of memory reserved for the host depends on the host operating system and the size of the host computer's memory.

If you are pushing close to the supported memory limits, the virtual machine might not power on after you power it off, and change settings in the virtual machine settings editor, particularly if you increase the virtual machine's memory size. If this happens, close the console in which you tried opening the virtual machine, and open a new console. The virtual machine should power on.

Specifying How Much Memory is Used by All Running Virtual Machines
You can set is the amount of host RAM that VMware Server is allowed to reserve for all running virtual machines. To set this parameter, choose Host > Settings > Memory. You must be user to change these settings.

The reserved memory setting specifies a maximum amount of host RAM that VMware Server is allowed to use. But this memory is not allocated in advance. Even if multiple virtual machines are running at the same time, VMware Server may be using only a fraction of the RAM you specified here. Any unused RAM is available for use by other applications. If all the RAM you specify here is in use by one or more virtual machines, the host operating system cannot use this memory itself or allow other applications to use it.

Virtual Machine Overhead
Virtual machines require relatively large amounts of memory to operate with reasonable performance. An individual virtual machine can use at most the amount of memory specified in its configuration file plus some overhead. The amount of overhead memory required depends upon the size of the guest's virtual disks, its behavior and the amount of memory allocated to the virtual machine. Refer to the table below for the typical upper limit needed, based on the amount of memory allocated to the guest.

Virtual Machine Memory ------- Overhead
Up to 512MB ------- Up to 54MB
Up to 1000MB ------- Up to 62MB
Up to 2000MB ------- Up to 79MB
Up to 3600MB ------- Up to 105MB


The amount of RAM actually used for a particular virtual machine varies dynamically as a virtual machine runs. If multiple virtual machines run simultaneously, they work together to manage the memory.

The recommended amount of RAM to specify for all running virtual machines is calculated on the basis of the host computer's physical memory and is displayed in the memory settings control ? Host > Settings > Memory. If you want VMware Server to use more or less physical memory, use this slider to change the amount.

If you set this value too high, the host may thrash if other applications are run on the host. If you set this value too low, virtual machines may perform very poorly and you cannot run as many virtual machines at once.

 
I know that windows does 2GB/2GB or 1GB/3GB (with /3gb boot switch) splitting for kernel memory vs program memory, I assume Linux has a similar requirement. Does this affect VMWare Server at all?
Click to expand...

That's irrelevant, the split is for virtual addresses not physical.

Host operating systems do not behave well when they run low on free memory for their own use. When a Windows or Linux host operating system does not have enough RAM for its own use, it thrashes ? constantly swaps parts of itself between RAM and its paging file on disk. To help guard against virtual machines causing the host to thrash, VMware Server enforces a limit on the total amount of RAM that can be consumed by virtual machines.
Click to expand...

While technically true, Windows does a lot more thrashing. But the other side of that coin is that while Linux will generally perform better as the host OS, if it does indeed run out of memory the OOM killer will come in and kill a process that the kernel decides is causing the memory problems and if you're running VMWare chances are pretty good that it'll get chosen. But if you're smart about it you should be fine, make sure the host OS has enough memory and don't run anything big on the host like Firefox unless you're sure you have the memory available.
 
Originally posted by: Nothinman
I know that windows does 2GB/2GB or 1GB/3GB (with /3gb boot switch) splitting for kernel memory vs program memory, I assume Linux has a similar requirement. Does this affect VMWare Server at all?
Click to expand...

That's irrelevant, the split is for virtual addresses not physical.

Host operating systems do not behave well when they run low on free memory for their own use. When a Windows or Linux host operating system does not have enough RAM for its own use, it thrashes ? constantly swaps parts of itself between RAM and its paging file on disk. To help guard against virtual machines causing the host to thrash, VMware Server enforces a limit on the total amount of RAM that can be consumed by virtual machines.
Click to expand...

While technically true, Windows does a lot more thrashing. But the other side of that coin is that while Linux will generally perform better as the host OS, if it does indeed run out of memory the OOM killer will come in and kill a process that the kernel decides is causing the memory problems and if you're running VMWare chances are pretty good that it'll get chosen. But if you're smart about it you should be fine, make sure the host OS has enough memory and don't run anything big on the host like Firefox unless you're sure you have the memory available.
Click to expand...


I should have noted in my above post that is quoted from the Vmware Server's Help file


 
Originally posted by: Nothinman
While technically true, Windows does a lot more thrashing. But the other side of that coin is that while Linux will generally perform better as the host OS, if it does indeed run out of memory the OOM killer will come in and kill a process that the kernel decides is causing the memory problems and if you're running VMWare chances are pretty good that it'll get chosen. But if you're smart about it you should be fine, make sure the host OS has enough memory and don't run anything big on the host like Firefox unless you're sure you have the memory available.
Click to expand...

Hmm...so my VMware could die all of a sudden without notice? I guess I don't really have a choice but I could at least do a soft shutdown. Is there any way to be notified if it's about to be killed?
 
Hmm...so my VMware could die all of a sudden without notice? I guess I don't really have a choice but I could at least do a soft shutdown. Is there any way to be notified if it's about to be killed?
Click to expand...

There will be stuff in the kernel logs after it's killed, but nothing before.
 
I've run VMWare server on a on a 512 MB CentOS server, hosting a CentOS server and a Windows server, and never had thrashing problems or killed vmware. They ran fine for months with no reboots.
 
Originally posted by: Nothinman
Hmm...so my VMware could die all of a sudden without notice? I guess I don't really have a choice but I could at least do a soft shutdown. Is there any way to be notified if it's about to be killed?
Click to expand...

There will be stuff in the kernel logs after it's killed, but nothing before.
Click to expand...


Also, if I gave the host OS a decent amount of swap (say 2GB), this would only happen if both memory was full and swap was full, correct? So a big swap file would prevent this problem at the expense of disk space?



 
Also, if I gave the host OS a decent amount of swap (say 2GB), this would only happen if both memory was full and swap was full, correct? So a big swap file would prevent this problem at the expense of disk space?
Click to expand...

Probably, but you still don't want to over commit the host OS, it'll make everything perform like crap.
 
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