This slideshow demonstrates the use of VMScluster composed of two virtual VAX nodes, each running on 8-processor virtual VAX.

We used this configuration during VAX MP development to stress-test the integrity of network operations, specifically correct functioning of memory barriers when XQDRIVER running on VAX processors and DEQNA/DELQA Ethernet controller access control memory area shared by them (BDL). The test also verifies integrity of other operations in the system.

To perform the test, we run a program that performs intensive IO to the files on the hard drive or drives served by the other VMScluster node and checks that results of IO operations performed across the cluster match expected data. Test program performs reads and writes wth modifier option that disables the use of VIOC cache, so read and written data is not cached on the local or remote node in file system extent cache, but rather gets written directly to and read back from the virtual hard drive. The test therefore also exercises the integrity of communication between the CPUs and MSCP disk controllers via UQSSP control area (that also relies on proper memory fences), as well as many other paths and components in the system.

We typically run multiple instances of test program on both nodes, so multiple operations are performed in parallel, and also IO operations are performed in crossfire fashion between the two nodes, at high rate. Data is transferred in small blocks (512 bytes per request), with the focus being not on the size of the payload, but rather high rate of operations intended to causing collisions during access to shared memory area, and verifcation of integrity in face of such collisions.

The cluster in this demo is accessed from DEC VT320 terminal connected to DECserver 200/MC booted from the cluster.

Let’s have a look at host machines:

At the bottom is PC with quad-core i7 3.2 GHz processor running Windows 7. This host machine runs VMScluster node VXA. Since each of i7 cores is hyperthreaded, host system has total of 8 logical CPUs and we can configure VAX instance with up to 8 virtual CPUs. Sitting on the top is Mac Mini server with quad-core i7 processor runnng OS X. It runs cluster node VXB. For further slides please click "next" in the navigation bar at the top.