IBM DS8700, Introduction And Planning Manual

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volumes between tiers. For example, if a volume is 1 TB, you do not want to move
the entire 1 TB volume when the generated heat map indicates that only 10 GB is
considered hot. This capability makes use of your higher performance tiers while
reducing the number of drives that you need to optimize performance.
Using automatic mode, you can use high performance storage tiers with a much
smaller cost. This means that you invest a small portion of storage in the
high-performance storage tier. You can use automatic mode for relocation and
tuning without the need for your intervention, using automatic mode to help
generate cost-savings while optimizing your storage performance.
Three-tier automatic mode is supported with the following Easy Tier functions:
v Support for ESE volumes with the thin provisioning of your FB volumes.
v
Support for a matrix of device (DDM) and adapter types
v Enhanced monitoring of both bandwidth and IOPS limitations
v
Enhanced data demotion between tiers
v Automatic mode hot spot rebalancing, which applies to the following auto
performance rebalance situations:
– Redistribution within a tier after a new rank is added into a managed pool
– Redistribution within a tier after a rank is removed from a managed pool
– Redistribution when the workload is imbalanced on the ranks within a tier of
a managed pool.
To help manage and improve performance, Easy Tier is designed to identify hot
data at the subvolume or sub-LUN (extent) level, based on ongoing performance
monitoring, and then automatically relocate that data to an appropriate storage
device in an extent pool that is managed by Easy Tier. Easy Tier uses an algorithm
to assign heat values to each extent in a storage device. These heat values
determine on what tier the data would best reside, and migration takes place
automatically. Data movement is dynamic and transparent to the host server and
to applications using the data.
By default, automatic mode is enabled (through the DS CLI and DS Storage
Manager) when the Easy Tier license feature is activated. You can temporarily
disable automatic mode.
Easy Tier provides extended and improved capabilities to support the automatic
functions of auto-rebalance, warm demotion, and cold demotion. This now
includes support for extent pools with three tiers (SSD, SAS Enterprise, or
Near-line SAS for DS8800 and SSD, FC, or SATA for DS8700).
With the latest enhancements to Easy Tier you can use automatic mode to help you
manage the thin provisioning of your ESE FB volumes.
Functions and features of Easy Tier: automatic mode
This section describes the functions and features of Easy Tier in automatic mode.
Auto-rebalance
Rebalance is a function of Easy Tier automatic mode to balance the extents in the
same tier based on usage. Auto-rebalance is now enhanced to support single
managed pools as well as hybrid pools. You can use the Storage Facility Image
(SFI) control to enable or disable the auto-rebalance function on all pools of an SFI.
Chapter 3. Data management features
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