Some limitations exist if you use the Easy
Tier® function on your
system.
- The Easy Tier® function supports the following tiered storage configurations:
- Local (internal) Serial Attached SCSI (SAS) flash drives in a storage pool with local
(internal) Serial Attached SCSI (SAS) hard disk drives (HDDs).
- Local (internal) Serial Attached SCSI (SAS) flash drives in a storage pool with
Fibre Channel-attached hard disk drives (HDDs).
- External Fibre Channel-attached flash drives in a storage pool with local
(internal) Serial Attached SCSI (SAS) hard disk drives (HDDs).
- External Fibre Channel-attached flash drives in a storage pool with
Fibre Channel-attached hard disk drives (HDDs).
- To ensure optimal performance, all MDisks in a storage pool tier must have the same technology
and performance characteristics.
- Easy Tier® automatic data
placement is not supported on volume copies that are image mode or sequential. I/O monitoring for
such volumes is supported, but you cannot migrate extents unless you convert the image or sequential
volume copies to striped volumes.
- Automatic data placement and extent I/O activity monitors are supported on each copy of a
mirrored volume. The Easy Tier®
function works with each copy independently of the other copy. For example, you can enable or
disable Easy Tier® automatic data
placement for each copy independently of the other copy.
- The
system creates new volumes or volume expansions by using extents from the enterprise tier, if
possible. However, if necessary, the system uses extents from the tier 0 flash, tier 1 flash, or
nearline tiers.
- When a volume is migrated out of a storage pool that is managed with the Easy Tier® function, Easy Tier® automatic data placement
mode is no longer active on that volume. Automatic data placement is also turned off while a volume
is being migrated between two pools that have Easy Tier® automatic data placement
enabled. Automatic data placement for the volume is reenabled when the migration completes.
Limitations when removing an MDisk by using the force
parameter
When an MDisk is deleted from a storage pool with
the force parameter, extents in use are migrated
to MDisks in the same tier as the MDisk being removed, if possible.
If insufficient extents exist in that tier, extents from the other
tier are used.
Limitations when migrating extents
When Easy Tier® automatic data
placement is enabled for a volume, the migrateexts command-line interface (CLI)
command cannot be used on that volume.
Limitations when migrating a volume to another storage
pool
When the
system migrates a volume to a new storage pool, Easy Tier® automatic data placement
between the generic flash drive tier and the Flash, Enterprise, or Nearline tier is temporarily
suspended. After the volume is migrated to its new storage pool, Easy Tier® automatic data placement
between the generic flash drive tier and the Flash, Enterprise, or Nearline tier resumes for the
newly moved volume, if appropriate.
When the
system migrates a volume from one storage pool to another, it attempts to migrate each extent
to an extent in the new storage pool from the same tier as the original extent. In some cases, for
example when the target tier is unavailable, the other tier is used. For example, the generic flash
drive tier might be unavailable in the new storage pool.
If the automatic data placement is enabled in the new storage pool, pending Easy Tier® status changes are assigned
after the volume completes its move to the new storage pool. Although the status changes are based
on volume use in the old storage pool, the new status is honored in the new storage pool.
Limitations when migrating a volume to image mode
Easy Tier® automatic data
placement does not support image mode. No automatic data placement occurs in this situation. When a
volume with Easy Tier® automatic
data placement mode active is migrated to image mode, Easy Tier® automatic data placement
mode is no longer active on that volume.
The Easy Tier® function does support evaluation mode for image mode volumes.