Changing Segment Size

Use this option to change the segment size on a selected logical drive. During this operation, I/O performance is affected but your data remains available.

How Long Does a Change Segment Size Operation Take?

The operation is slower than other modification operations (for example, changing RAID levels or adding free capacity to an array) because of the way the data is physically reorganized and because of the temporary internal backup procedures that occur during the operation.

The specific amount of time a Change Segment Size operation can take depends on many variables, including the I/O load from the hosts, the modification priority of the logical drive, the number of drives in the array, the number of drive channels, and the processing power of the Storage Subsystem controllers.

If you want this operation to complete faster, you can change the modification priority, although this may decrease system I/O performance. To change the priority, select a logical drive in the array, then select Logical Drive >> Properties.

Important:

When to Change Segment Size

A default segment size is set during logical drive creation, based on the array RAID level and the logical drive usage you specify. These two parameters should optimize the segment size appropriately for your environment. However, it is important to monitor your Storage Subsystem and change segment size when necessary for optimal performance based on the guidelines below.

If your typical I/O size is larger than your segment size, increase your segment size in order to minimize the number of drives needed to satisfy an I/O request. This is especially true in a multi-user, database or filesystem storage environment. Using a single drive for a single request leaves other drives available to simultaneously service other requests.

If you are using the logical drive in a single-user, large I/O environment, such as for multimedia application storage, performance is optimized when a single I/O request can be serviced with a single data stripe (the segment size multiplied by the number of drives in the array that are used for I/O). In this case multiple disks are used for the same request, but each disk is only accessed once.


How to Change Segment Size

1 Select a logical drive in the Logical View; then select either (1) the Logical Drive >> Change Segment Size pull-down menu option, or (2) Change Segment Size from the right-mouse pop-up menu.

Result: The flyout menu of segment sizes is displayed. The current segment size is marked with a black dot to its left. Any segment sizes that are not appropriate for the array RAID level are not available.
2 Select the desired segment size.

Result: The Change Segment Size Confirmation dialog box appears.
3 Select Yes.

Result: The segment size modification operation begins. The logical drive icon in the Logical View will show an Operation in Progress status while the operation is taking place.

Note: To view the progress or change the priority of the modification operation, select a logical drive in the array, then select Logical Drive >> Properties.