It can exercise the OSS either locally or remotely via the network.
The script uses lctl::test_brw to drive the echo_client doing sequential
-I/O with varying numbers of threads and objects. One instance of lctl is
-spawned for each OST.
+I/O with varying numbers of threads and objects (files). One instance of
+lctl is spawned for each OST.
Running
I've found it most useful to import the summary data (it's fixed width)
into Excel (or any graphing package) and graph bandwidth v. # threads for
-varying numbers of concurrent regions. This shows how the device performs
-with varying queue depth. If the series (varying numbers of concurrent
-regions) all seem to land on top of each other, it shows the device is
-phased by seeks at the given record size.
+varying numbers of concurrent regions. This shows how the OSS performs for
+a given number of concurrently accessed objects (i.e. files) with varying
+numbers of I/Os in flight.
+
+It is also extremely useful to record average disk I/O sizes during each
+test. These numbers help find pathologies in file the file system block
+allocator and the block device elevator.