Virtual band-width

[Griff]

Hopefully a trivial question to answer....

If I have two virtual servers on the same host, what aspects would limit the
effective bandwidth between the two virtual machines, or between the machine
and the host?

I'd like these to emulate 1 GBit cross-over cables if at all possible.

(running Host Win2000 server, Guest Win 2000 server, GSX 3.1.0)

[CBee]

Post by Griff
Hopefully a trivial question to answer....
If I have two virtual servers on the same host, what aspects would limit the
effective bandwidth between the two virtual machines, or between the machine
and the host?

The VMNet is only limited by connected hardware:

If a vmnet is connected to a physical, 10 MBit nic, this nic is limiting the
bandwidth.

If it is a 100 MBit nic, it is most likely to be limiting the bandwidth to 100
MBit.

If it is a 1GBit nic, other parts of the system can become the bottleneck.

If there is no physical nic, other parts of the system are the bottleneck.

In the end, if you use the host-only networking, the communication between the
guests (and the host) is only limited by the speed the processes can dump data
in the nic.

Things that might limit the communication include:
- CPU speed (to boost the data)
- number of CPUs (to avoid swapping of guests)
- memory speed (where data is form memory or buffered)
- disk speed (if data comes from disk)

Post by Griff
I'd like these to emulate 1 GBit cross-over cables if at all possible.

????

Post by Griff
(running Host Win2000 server, Guest Win 2000 server, GSX 3.1.0)

These OSes will inform you about the bandwidth of the nics used. This is just a
number that is coded into the driver. Specially with the older vmware-nic (the
10MBit one) I've seen measurements that are way beyond the scale. I don't recall
by head the advertised bandwidth of the new nic. But do expect it to get beyond
that speed.


CBee

[kirk mears]

the system bus speed actually determines network bandwidth between the two
VM's once all hardware bottlenecks (drive speed, memory speed, CPU speed)
are removed from the equation.

i have personally seen throughput higher than 100% of a 10Mb connection on a
VM (timing the file transer)

hope that helps

you can actually obtain higher throughput than what you see (copy a file
from one VM to the other and time it to determine actual bandwidth)

kirk

Post by CBee

Post by Griff
Hopefully a trivial question to answer....
If I have two virtual servers on the same host, what aspects would limit the
effective bandwidth between the two virtual machines, or between the machine
and the host?

If a vmnet is connected to a physical, 10 MBit nic, this nic is limiting
the bandwidth.
If it is a 100 MBit nic, it is most likely to be limiting the bandwidth to
100 MBit.
If it is a 1GBit nic, other parts of the system can become the bottleneck.
If there is no physical nic, other parts of the system are the bottleneck.
In the end, if you use the host-only networking, the communication between
the guests (and the host) is only limited by the speed the processes can
dump data in the nic.
- CPU speed (to boost the data)
- number of CPUs (to avoid swapping of guests)
- memory speed (where data is form memory or buffered)
- disk speed (if data comes from disk)

Post by Griff
I'd like these to emulate 1 GBit cross-over cables if at all possible.

????

Post by Griff
(running Host Win2000 server, Guest Win 2000 server, GSX 3.1.0)

These OSes will inform you about the bandwidth of the nics used. This is
just a number that is coded into the driver. Specially with the older
vmware-nic (the 10MBit one) I've seen measurements that are way beyond the
scale. I don't recall by head the advertised bandwidth of the new nic. But
do expect it to get beyond that speed.
CBee