HP 3PAR InForm OS 3.1.1 CLI Administrator's Manual

Restarting a Volume Modification Task
Restarting a tunevv task restarts a task that was previously interrupted. You may choose to restart
a tunevv task if the operation was interrupted because of:
• User-initiated cancellation of a task.
• Component failure.
• To restart a tunevv task, issue the tunevv restart <VV_name> command.
Tuning Physical Disks
HP 3PAR System Tuner Software is an optional feature that improves performance by identifying
over-used physical disks, and performing load balancing on those disks without interrupting access.
Use the tunepd command to perform tuning tasks on physical disks. You must purchase the HP
3PAR System Tuner Software license to use the tunepd command.
If the performance of one or more physical disks degrades, the throughput of the logical disks is
reduced and the entire system performance may decline. There are two general reasons why a
physical disk may have degraded performance:
• The physical disk has reached its maximum throughput due to an unbalanced load. A disk in
this state typically has unusually high average service times when compared to other disks.
• The physical disk is a bad disk. A bad disk typically has unusually high maximum service
times when compared to other disks.
The tunepd command allows you to:
• Perform physical disk performance tuning on an entire system or on a specified subset of disks.
• Set performance thresholds for physical disk tuning.
• Identify and relocate under-performing chunklets.
In the following example, physical disks with average service times exceeding 50 milliseconds are
identified and their chunklets are automatically relocated to rebalance the load on the physical
disks.
• To tune physical disks, issue the tunepd -vvlayout -chstat -movech auto avgsvct
50 command, where:
◦ <vvlayout> specifies that the layout of the virtual volume is displayed.
◦ <chstat> specifies that chunklet statistics are displayed.
◦ <movech> specifies that if any disks with unbalanced loads are detected, the chunklets
are moved from those disks for load balancing
◦ <auto> specifies that the system automatically chooses source and destination chunklets.
◦ <avgsvct> specifies the average service time threshold in milliseconds.
For more information about viewing system performance statistics, see “Viewing Statistics and
Histograms” (page 118). For more information about how the system manages space usage, see
the HP 3PAR InForm OS Concepts Guide.
NOTE: Running the tunepd command does not eliminate the need to run the tunesyscommand.
The tunesys command performs space based balancing. The tunepd command performs service
time and I/O based balancing.
Tuning Physical Disks 149