I am running two virtual machines on a brand new Dell PowerEdge T310 server running ESXi 4.0 (fully patched). One of the VM's is Windows XP Pro (long story) and the other is Mandriva Linux 2010.0. We've been having some performance issues on the Linux Vm since day one. At first I thought it was the new hardware or something in the setup of ESXi but having found no problems there I decided to test similar scenarios on the XP machine and found the issue not to exist there.
The problem as I see it is that I can transfer a 500MB file to a share on the XP machine at around 22MB/sec (to or from, similar performance). However, transferring to the Linux machine goes at around 3MB/sec. What's more, copying a file from partition to partition on the Linux machine has about the same performance, 3MB/sec (and sometimes worse.)
I looked at the configuration of both the virtual machines and the disks don't seem to be configured differently, so I ruled out that the problem is with the host. The host can obviously have a VM that performs as expected.
I have looked at /etc/fstab to see if there was anything odd there but I don't see anything out of the ordinary. I ran iotop and saw about 1200 KB/sec reads and writes while copying a very large file from partition to partition, and using about 16% of the IO, but there didn't seem to be anything else there that wasn't a 0.00 B/sec (other than now and then a very quick write to syslog or such).
The one thing I can think of that seems out of the ordinary is when i am running a mv or cp command, it shows in "top" as using 67 %CPU which seems rather high.
Is it possible that CPU speed is the problem? The server has an Intel i3 530 CPU @ 2.93 GHz, with 4MB of cache. I configured this virtual machine with 4 virtual CPU's (the maximum allowed) while the XP VM that is working just fine I configured with only 1 virtual CPU.
Any clues? This is driving us crazy. We run an SQL database on this machine that is about twice as slow on the new hardware as it used to be on a 7 year old Pentium 4 server.
I'd appreciate any help or even just ideas.