Automatic data placement

When IBM® Easy Tier® is active, the system completes several functions to automatically place data in the appropriate storage tier. Easy Tier measures the host access activity to the data on each storage extent. It also provides a mapping that identifies high activity extents, and then moves the high-activity data according to its relocation plan algorithms.

To automatically relocate the data, Easy Tier initiates the following processes:

Monitors volumes for host access to collect average usage statistics for each extent over a rolling 24-hour period of I/O activity.
Analyzes the amount of I/O activity for each extent to determine whether the extent is a candidate for migrating to or from the higher performing flash drive tier.
Develops an extent relocation plan for each storage pool to determine exact data relocations within that storage pool. Easy Tier then automatically relocates the data according to the plan.

While it relocates volume extents, Easy Tier follows these actions:

Attempts to migrate the most active volume extents first.
Refreshes the task list as the plan changes. The previous plan and any queued extents that are not yet relocated are abandoned.

Automatic data placement is enabled by default for storage pools with more than one tier of storage. When you enable automatic data placement, by default all striped volumes are candidates for automatic data placement. Image mode and sequential volumes are never candidates for automatic data placement. When automatic data placement is enabled, I/O monitoring is undertaken for all volumes whether or not the volume is a candidate for automatic data placement. When automatic data placement is enabled and sufficient activity warrants relocation, extents will be relocated within a day after enablement. You can control whether Easy Tier automatic data placement and I/O activity monitoring is enabled or disabled by using the settings for each storage pool and each volume. Each command in the following list that can create or change the settings for storage pools can enable or disable both Easy Tier functions. Any command that can create or change the settings for volumes can enable or disable automatic data replacement, if automatic data replacement is enabled for the storage pool. You can control or view automatic data placement by using the following command-line interface (CLI) commands:

addvdiskcopy: Adds a copy to an existing volume by changing a nonmirrored volume into a mirrored volume.
chmdiskgrp: Modifies the properties of the storage pool. Use this command to turn on Easy Tier evaluation mode or I/O monitoring and to turn off Easy Tier functions on a storage pool with more than one tier of storage.
Note: When automatic data placement is active on a storage pool, set a warning threshold for the storage pool. Automatic data placement cannot function if the storage pool is used 100%.
chvdisk: Modifies the properties of a volume.
lsmdiskgrp: Lists storage pool information.
lsvdisk: Lists volume information.
lsvdiskcopy: Lists volume copy information.
mkmdiskgrp: Creates a storage pool.
mkvdisk: Creates sequential, striped, or image mode volumes.

If you want to disable automatic data placement for a volume or storage pool, set the easytier attribute to off.