Here are my assumptions and speculations:
1. I am assuming that you are sending the data from a partition to the other using the same processor and two physical NICs.
2. It runs slower on the virtual machine because all the work of emulating the IP stack and actually moving the data is performed over the same processor (or set of processors). In contrast, when you do it over a physical network, you have the auxiliary I/O coprocessors of the network cards doing the job. Considering that you have a 2Gb link, the actual transport of the data is no longer a concern that might limit your transmission speed.
3. Well, I'm speculating that the disk is the bottleneck, because we know that the network is not the bottleneck, and the disk is typically the bottleneck in most situations. Is the disk actually the bottleneck? Maybe not.
Continuing with this train of thought, perhaps if you could find what is the subsystem/job emulating the virtual network interface, you could tweak the job to give it a better priority or a larger time slice.
Luis
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Ingvaldson, Scott
Sent: Thursday, January 24, 2008 5:24 PM
To: Midrange Systems Technical Discussion
Subject: RE: Virtual Ethernet - Part II
I'm having a hard time believing that disk is the bottleneck here. That
would make the VLAN run at the same speed as the network, not slower.
And I wouldn't be able to save this 60 GB library to a save file in
under 3 minutes.
My apples to apples comparison run today:
FTP over VLAN: 59521118976 bytes transferred in 4777.693 seconds.
Transfer rate 12458.129 KB/sec.
FTP over network: 59521118976 bytes transferred in 3808.596 seconds.
Transfer rate 15628.102 KB/sec.
Does anyone have any insight into the VLAN configuration or at least
some real world performance numbers?
Regards,
Scott Ingvaldson
Senior IBM Support Specialist
Fiserv Midwest
-----Original Message-----
From: Luis Colorado [mailto:LuisC@xxxxxxxxxxxxxxxx]
Sent: Thursday, January 24, 2008 9:25 AM
To: Midrange Systems Technical Discussion
Subject: RE: Virtual Ethernet - Part II
Well, if you think about it, 21577 Kbytes/sec is roughly equivalent to
169 Mbits/sec, meaning that your transfers through the network were
using less than 10% of your 2Gb/sec network. Years ago, with 10Mbit/sec
and 100Mbit/sec network speeds, clearly the bottleneck was the network.
However, with your 2Gb/sec connections, your bottleneck is now your
system (more specifically, your disk).
So, bottom line (and I don't know much about VLAN optimization), I would
say that this is as good as it gets.
-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Ingvaldson, Scott
Sent: Thursday, January 24, 2008 10:00 AM
To: midrange-l@xxxxxxxxxxxx
Subject: Virtual Ethernet - Part II
OK, the VLAN appears to be working as designed but I still have some
questions.
The speed of our Anynet transfers has increased by a factor 4 - 8.
Transfers that were taking 3 - 4 hours now complete in 30 - 45 minutes.
As long as I do them one at a time. If I do more than one at a time
they slow considerably.
FTP transfers take the same amount of time using the VLAN as they did
running over the network. Reported transfer rates are in the range of
12000 - 14000 KB/sec. Strangely enough, I was able to hit 21577 KB/sec.
on a 2 GB transfer, not using the VLAN, doing an FTP to a Network
Server!
An iNav monitor shows the VLAN utilization to be 8 - 10% when doing FTP
and up to 20% for SAVRSTxxx commands. But if I run two simultaneous
SAVRSTxxx transfers the utilization drops to 15%, even if the transfers
are initiated from different LPARs.
Is there some tuning that can be done to the VLAN or is this as good as
it gets?
Regards,
Scott Ingvaldson
Senior IBM Support Specialist
Fiserv Midwest
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