On Tue, Jul 17, 2012 at 7:50 PM, Alan Altmark <[email protected]>wrote:
> > Perhaps there is a misunderstanding. I have no objection to real > HiperSockets for backups (or any other reason) as long as you realize that > HiperSockets consume z CPU cycles since it is the CPU that moves the data, > not the IOPs. > > Anything that moves packets will cost CPU cycles, in the Linux TCP/IP stack and in CP. The biggest factor is the number of packets, so 56K packets on HiperSockets is hard to beat in comparison with 1500 byte on the LAN. A virtual NIC (connected to a VSWITCH or Guest LAN) is some 50% more expensive than using HiperSockets. When using a Linux guest as virtual router, things do add up rather fast (packets are handled 3 times, plus the cost of the virtual router). Whether these aspects should play a major role in your network design really depends on the data volume. Many servers don't transfer hundreds of GB's per day. I would suggest to use a network design that makes sense and measure your CPU cost and network volume to see whether you need to connect some of the busy guests differently. Rob -- Rob van der Heij Velocity Software http://www.velocitysoftware.com/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
