IBM System Storage DS3000, Programming Manual

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Chapter 6. Using the Enhanced FlashCopy Images Premium
Feature
Note: The Enhanced FlashCopy premium feature is available only on the DS3500, DCS3700, and
DCS3700 storage subsystem with Performance Module Controllers storage subsystems. In this
publication, the Enhanced FlashCopy premium feature and its associated functions will always have the
words
Enhanced FlashCopy as prefix. Examples of this feature include:
v Enhanced FlashCopy image
v Enhanced FlashCopy groups
v Enhanced FlashCopy repository drive
The current FlashCopy premium feature and its features will have only the word
FlashCopy
as a prefix.
Examples of this feature include:
v FlashCopy logical drive
v FlashCopy repository drive
Controller firmware version 7.83 and later supports a new version of FlashCopy, called Enhanced
FlashCopy. Enhanced FlashCopy provides new ways of creating a large number of FlashCopies of a base
logical drive, with minimum performance degradation due the
copy-on-write operations feature. In an
existing FlashCopy operation, a
Copy-on-write
operation will be performed for each FlashCopy of the
base logical drive. The higher the number of FlashCopies, the higher the number of
copy-on-write
operations. In an Enhanced FlashCopy operation, only one
copy-on-write
operation will be performed
for a group of up to 32 FlashCopies of a base logical drive. Up to 32 Enhanced FlashCopy images of a
base logical drive can be grouped into an Enhanced FlashCopy group with an Enhanced FlashCopy
group repository drive.
An Enhanced FlashCopy image is a logical image of the content of an associated base logical drive
created at a specific moment. An Enhanced FlashCopy image can be thought of as a restore point. A host
cannot directly read from or write to the Enhanced FlashCopy image because the Enhanced FlashCopy
image is used to save only the transient data captured from the base logical drive.
You must create an Enhanced FlashCopy logical drive to enable host access to a complete copy of the
data contained in the Enhanced FlashCopy image. The Enhanced FlashCopy logical drive contains its
own repository, which is used to save any subsequent modifications made by the host to the base logical
drive without affecting the referenced Enhanced FlashCopy image.
Enhanced FlashCopy images are useful any time you need to be able to roll back to a known good data
set at a specific point in time. For example, before performing an operation on a logical drive that you
might want to reverse, you can create an Enhanced FlashCopy image to enable the reverse operation and
restore the entire logical drive to its previous state. An Enhanced FlashCopy image is created almost
instantaneously, and initially uses no disk space, because it stores only the incremental changes needed to
roll the logical drive back to the point-in-time when the Enhanced FlashCopy image was created.
You can create Enhanced FlashCopy images manually or automate the process with a schedule. With a
schedule, an Enhanced FlashCopy image is generated automatically, based on the date and time you
choose, and is displayed with its associated Enhanced FlashCopy group. You can create Enhanced
FlashCopy images for these storage objects:
v
Standard logical drives
A standard logical drive has a fixed physical capacity that is entirely reserved for the data on the
logical drive.
v
Thin logical drives
© Copyright IBM Corp. 2008, 2012
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