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We are experiencing performance issues with a VMware Server 2.x installation on an Ubuntu 8.04 host. When the host system is generating IO load (for example, copying large files as part of a backup operation), the guests (also Ubuntu 8.04) become extremely unresponsive and slow (simple Apache HTTP requests taking 5 seconds instead of the usual 200ms).

We tried optimizing various aspects of the VMs, but the issue remains. Is there a known bug with VMware performance under linux if host IO load is high? Is there a way to fix this? Is this only an issue with Ubuntu systems, or have you seen it on other systems before? Thanks!

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What's the system setup like? No of disks, type of controller\raid setup, CPU\RAM on the host and how many guests and their config. – Helvick Apr 23 '10 at 18:23

Is there a reason you're running VMware Server instead of ESXi? ESXi is free, and will give you significantly better performance, both in terms of Disk/Network IO as well as CPU and memory performance as well.

What you're seeing is is pretty normal - you're getting high levels of IO contention on the host and everybody is being forced to wait their turn for the physical resources of the server. To fix this, consider moving to ESX, ESXi, or possibly using faster hard drives.

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We use VMware Server instead of ESX because we need full control over the host system (i.e. firewall, backup scripts, other maintenance stuff) and my understanding is that you wouldn't be able to do all this with ESX (at least not as easily as you could do with a standard Linux host system). We successfully used VMware Server on a Windows host for years (even on a much slower system) and never had any problems, even under IO load, so I suspect there is a real bug/configuration issue somewhere. – Dennis G. Apr 21 '10 at 18:58
With ESXi you would have a problem if you wanted to do all this on the host but in general you don't want to, the idea behind ESXi is that it has a minimal attack surface and is simple to backup remotely. With the full version of ESX you have a CentOS\RH derived Service Console where you can do all this but it is not free. – Helvick Apr 23 '10 at 18:27

Some of these VMWare Server on Ubuntu optimisations I have put together from experience maybe useful to you:

I have also encountered issues with the performance of Ubuntu's default software RAID configuration. This may not apply to you, but if you are running a software RAID with Ubuntu, this configuration change may help:

Finally there are some very useful command line I/O monitoring tools that are worth checking out. The sysstat package in apt has the iostat tool which is very handy. Plus, the vmstat tool is also useful for checking out what your CPU is up to and/or waiting for during high I/O loads.

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This is normal to a busy VM guest system.
The system slows down, the load increases...
Consider moving to a normal server.

Let me know in case you find the cause.
I have this problem too.


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It's only normal if you have too many guests\excessive load on the host. Even with VMware Server you should be able to run multiple concurrent VM's and have the host working provided there are enough resources (CPU\Memory\Disk\Network) to go around. – Helvick Apr 23 '10 at 18:25

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