Ever since the availability of enterprise class Ethernet switches it has been possible to easily define one of the ports on those switches as a “mirror port”. A mirror port is a tremendously useful thing as it gets a read only copy of all of the traffic which goes through the switch sent to it. This enables a wide variety of management tools from low level network tools, to packet analyzers to applications performance management tools to collect their data without being directly in the data path. This approach has taken on even more prominence in the virtualized world since VMware discourages agents in guests, which makes collecting performance data via a virtual appliance on the virtual mirror port on the vSwitch (or the Cisco Nexus 1000V) the preferred method.
Articles Tagged with SAN Performance
Almost every enterprise that I have spoken to about their experiences in virtualizing anything more than simple or tactical applications has come across one or more that did not perform well once virtualized. In most cases these were applications that used low amounts of CPU and reasonable and predictable amounts of memory, so it stood to reason that resource conflicts in these areas were not the cause of the performance issues. Most of these enterprises had the network support for the virtualized hosts dramatically over-configured with multiple-teamed NIC’s and redundant HBA’s, so there was every reason to believe that the network was most likely not the issue either.