Overview Of Auto Lun; Limitations Of Auto Lun; Source And Target Volumes - HP XP P9500 User Manual

1 Overview of Auto LUN

This is an overview of manual and automatic Auto LUN.
Unless otherwise specified, the term P9000 in this guide refers to the following disk array:
P9500 Disk Array
The GUI illustrations in this guide were created using a Windows computer with the Internet Explorer
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Overview of Auto LUN
Auto LUN is used to optimize your data storage by balancing resource utilization and resolving
bottlenecks of system activity on the storage system. If heavy input/output (I/O) activity occurs on
a specific hard disk drive or disk processor, the host might suffer from slower response times. To
avoid this situation, Auto LUN lets you migrate high-usage volumes to a low-usage hard disk drive
or a fast hard disk drive.
Migrating volumes with Auto LUN is completely non-disruptive as the data being migrated can
remain online to all hosts for read and write operations throughout the entire migration process.
Auto LUN operations can be performed manually or set up to run automatically at specified times.
In manual migration, the system administrator specifies the source volume and the target volume,
and then executes the manual migration plan. In an "Auto" migration, the Auto LUN software
determines source and target parity groups based on Auto Plan settings and executes the migration
plan automatically at a specified interval and time.

Limitations of Auto LUN

You should keep in mind that Auto LUN operations can improve performance in one area while
decreasing performance in another. Consider the following scenario:
Parity Group A has an average usage value of 20%
Parity Group B has an average usage value of 90%
Through Auto LUN, it is estimated that if one volume from Parity Group B is migrated to Parity
Group A, the usage values of both parity groups become 55%. In this scenario, the I/O response
time for Parity Group B will most likely decrease, while the I/O response time for Parity Group A
will most likely increase. Overall, the throughput may increase or decrease.
Auto LUN should only be performed when you can expect a large improvement in storage system
performance. Auto LUN operations may not provide significant improvement for cases in which
parity group or volume usage varies only slightly, or for cases in which the overall MP or DRR
usages is relatively high.
When an error condition exists in the P9500 storage system, resource usage can increase or
become unbalanced. Do not use data collected during an error condition as the basis for planning
Auto LUN operations.

Source and target volumes

The Auto LUN source volume is the volume whose data will be migrated, and this data is migrated
to the Auto LUN target volume. For Auto Migration plans to be executed successfully, a sufficient
amount of target volume candidates must be reserved in each HDD class and parity group. In a
manual migration, the actual target volume must be reserved or the migration will fail. Theoretically,
the source and target volumes can be located anywhere in the storage system, however, there are
some restrictions for selecting source and target volumes in a manual migration. See
(page 10) for more information on requirements and restrictions when selecting source and target
volumes.
"Requirements"
Overview of Auto LUN 5