HP StorageWorks SAN Virtualization Services Platform Best Practices Guide (5697-0935, May 2011)

14 Remedies for SAN and SVSP issues
Setup virtual disk access times
Access to the VSM setup virtual disks can be monitored with the Windows Performance Monitor
tool. On a VSM server, Windows Performance Monitor includes an additional dedicated
performance object that the VSM agent adds during VSM software installation.
To launch Windows Performance Monitor, click Start > Programs > Administrative tools >
Performance (or Start > Run > Perfmon). The Windows Performance Monitor window opens with
a default display of three monitored objects (Pages/sec, Avg. Disk Queue Length, and % Processor
Time). To remove them, press Delete or click the delete icon (X).
Add the dedicated performance objects of the VSM agent. Click the + icon (or use Ctrl+I) to launch
the Add counters interface. From the Performance object drop-down list, locate "Sync. Mirror Group
Performance" and "Sync. Mirror Job Performance." Each performance object includes multiple
counters, and together they show the total and the specific performance for each synchronous
mirror group and jobs that run on the VSM server. For more information, see the "Monitoring the
SVSP domain" chapter in the HP StorageWorks SAN Virtualization Services Platform Administrator
Guide.
High application latency
Figure 19 (page 61) shows that as the objects approach saturation, the response time increases.
The SVSP SAN typically contains multiple fabrics, arrays, servers, and SVSP components, and any
object operating in this range will show less than optimal performance. SVSP is especially susceptible
to high application latency when operating in saturation. This area of the performance curve is
not where you want the SAN to operate, with the reasons described below.
Figure 19 Network operating ranges
SAN buffers
When a switch sends data to the SVSP, those buffers are not returned immediately as is the case
with an array which can save the data in NV cache. SVSP's flow-through architecture must hold
on to the switch buffers until that data is no longer in use.
SVSP command buffer
For the same reason stated above, a flood of commands directed at SVSP must be processed and
cannot be acknowledged until finished.
Setup virtual disk access times 61