Extremly high Harddisk read/write speed in Win 2003 VM

[turboloader]

Hello,

A few days ago I made a few harddisk benchmarks inside a Windows VM. Wether what program I'm using I always get nearly the same results.
How is it possible to get a transfer average of 450 MByte/s.
I don't know how to explain it. May be something with the mainmemory chaching instead of writing directly on the harddisk ? I hope some one has a right answer.

 

[dietmar]

May be something with the mainmemory chaching instead of writing directly on the harddisk ?

Lock like you are testing RAM speed ;-) I guess you need a better benchmark toolkit.

 

[turboloader]

Thanks ,
Some Idea for a Windows VM ? I tried a few for windows with no different results.

 

[dietmar]

All benchmarks I know are designed to benchmark physical disk. So they are not well suited to benchmark virtual disks.

 

[mechanicus]

I tested the virtual disks in Fedora10 (guest) with the dd command:

800MB writing: dd if=/dev/zero of=test.img bs=1024 count=800000

Then after a reboot for deleting the cache:
800MB reading: dd if=test.img of=/dev/null bs=1024

The performance in KVM (with the virtio driver) seem equal or a little better than in the ESXi

Best Regards mechanicus

 

[mangoo]

Hello,

A few days ago I made a few harddisk benchmarks inside a Windows VM. Wether what program I'm using I always get nearly the same results.
How is it possible to get a transfer average of 450 MByte/s.
I don't know how to explain it. May be something with the mainmemory chaching instead of writing directly on the harddisk ? I hope some one has a right answer.

It is likely that everything was served from cache, either:
- Proxmox VE host's cache, or
- guest system's cache - if it's this one, your benchmarking program is really bad

You can empty cache on the host with:

echo 3 > /proc/sys/vm/drop_caches

prior to doing any benchmark.