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The Auto LUN operation consists of two steps:
• Copy thedataonthe Auto LUNsourcevolumetothe Auto LUN target volume(see
Figure 7 on page 15).
•
Transfer host access to the target volume to complete the migration (see Figure 8 on page 16).
TheAutoLUN source volume canbeonlinetohosts during migration. Thetarget volumeisreservedprior
to migration to prevent host access during migration. The source and target volumes can be located
anywhere within the storage system.
The Auto LUN copy operation copies the entire contents of the source volume to the target volume cylinder
by cylinder (24 tracks at a time, not including the diagnostic and unassigned alternate tracks). If the
source volume is updated by write I/Os during the copy operation, the updates will be recorded on
the cylinder map of a volume. If there are deferential data formed by the update, the deferential data
will be copied from the source volume to the target volume and this will be repeated until all differential
data on the source volume is copied. However, there are upper limits to the number of times the copy
is executed and the limit depends on the capacity of the migrated volume. The limit increases as the
capacity of the migrated volume increases. When the deferential data still exists after copy is repeated to
the upper limit, the volume migration fails. Execute the migration by reducing the workloads between
hosts and the storage system. The indication of the workloads between hosts and the storage system must
be 50 IOPS or below for updating I/O.
When the volumes are fully synchronized (that is when there is no differential data on source volume), the
storage system completes the migration by swapping the reserve attribute (target is normal, source is
reserved) and redirecting host access to the target volume. Auto LUN performs all migration operations
sequentially (that is one volume migration at a time).
Note:
Approximate copy times with no other I/O activity are OPEN-3 = 1.5 min, OPEN-9 = 4.5 min,
OPEN-E = 9 min.
Note:
For manual migration operations, Auto LUN checks the current storage system write pending rate
and cancels a migration operation if the write pending rate is higher than 60%.
Hosts cannot access device. Hosts can access device.
Source
Volume
COPY
(24 tracks at
a time)
Target
Volume
LDEV ID = 0x123 LDEV ID = 0x321
Reserved
Figure 7 Data Flow during an Auto LUN Operation
XP24000 Auto LUN Software User's Guide
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