Initially, the repository logical drive has only a single standard logical drive, so its capacity is exactly that
of its single standard logical drive. The Enhanced FlashCopy group repository logical drive is expanded
by attaching additional standard logical drives. The capacity then becomes the sum of the capacities of all
of its concatenated logical drives. Operating in this manner provides a flexible and low-overhead capacity
expansion mechanism.
You can create an Enhanced FlashCopy repository logical drive automatically using the default settings or
you can manually create an Enhanced FlashCopy repository logical drive by defining the settings for the
repository logical drive.
After the Enhanced FlashCopy group and the associated repository logical drive are created, any write
operation on the base logical drive necessitates that the affected content of the base logical drive be saved
to a different location before it is overwritten by the new data. The Enhanced FlashCopy image
copy-on-write mechanism performs this task, and saves the required data to the repository logical drive.
An index in the Enhanced FlashCopy logical drive repository logical drive. is then updated to reflect the
new location of the Enhanced FlashCopy image content for the affected logical block addressing (LBA)
range. An ensuing base logical drive write to an LBA range that has already been preserved by a
previous copy-on-write operation does not require an additional copy-on-write action, so the overhead of
the copy is not repeated in such cases.
As an Enhanced FlashCopy group attribute, users can choose the way in which Enhanced FlashCopy
logical drive repository full conditions are managed through one of these modes of operation when such
conditions arises:
v
Auto-Purge Enhanced FlashCopy Images
:
Automatically delete the oldest Enhanced FlashCopy images in the Enhanced FlashCopy group to free
up space that can be used to satisfy the copy-on-write operation capacity needs in the Enhanced
FlashCopy group repository.
v
Fail Base Writes
Fail write requests to the base logical drive that triggered the Enhanced FlashCopy logical drive
repository access. In this case, the base logical drive, the Enhanced FlashCopy group and its Enhanced
FlashCopy images and Enhanced FlashCopy logical drives remain in their previous states.
Attention:
AIX does not support the
Fail writes to base logical drive
option of the Enhanced
FlashCopy logical drive repository full policy. Selecting this option might cause data loss on the base
logical drive. If you are using AIX, ensure that the default option
Fail FlashCopy logical drive
is
selected. Ensure you monitor the capacity of the FlashCopy repository logical drive, as you cannot
access the FlashCopy if the repository logical drive reaches full capacity.
Each Enhanced FlashCopy group can be configured independently in this regard. Expanding an
Enhanced FlashCopy logical drive repository logical drive does not directly change the state of any
Enhanced FlashCopy in the Enhanced FlashCopy group. In particular, Enhanced FlashCopy images in the
purged state remain in that state even after a repository logical drive expansion creates additional free
space for the Enhanced FlashCopy group.
Repository Logical drive Names
The Storage Manager GUI and CLI automatically provide a name (user label) every time a standard
logical drive is created for use as an Enhanced FlashCopy logical drive repository logical drive member.
The user label string consists of the prefix “
repos_
” followed by a four-digit, zero-padded numeric suffix.
The numeric value has a minimum value of
1
, and is selected using the smallest previously-unused
number among all existing logical drives. Users cannot modify or override the name that is automatically
provided by IBM DS Storage Manager software.
Note:
IBM DS Storage Manager software always uses a lower-case "
repos_
" prefix when it creates
Enhanced FlashCopy repository logical drives. IBM DS Storage Manager software tests the logical drive
6-4
IBM System Storage DS3000, DS4000, and DS5000: Command Line Interface and Script Commands Programming Guide
Summary of Contents for System Storage DS3000
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