HP StorageWorks XP Remote Web Console Software User Manual
Page 11
NOTE:
The storage system documents (including this manual) use the term source volumes to
refer to volumes that should be migrated. The term target volumes is used for volumes that should
become migration destinations.
The XP Auto LUN operation consists of two steps:
1.
Copy the data on the XP Auto LUN source volume to the XP Auto LUN target volume (see
).
2.
Transfer host access to the target volume to complete the migration (see
).
The XP Auto LUN source volume can be online to hosts during migration. The target volume is
reserved prior to migration to prevent host access during migration. The source and target volumes
can be located anywhere within the storage system.
The XP 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 differential data is formed by the
update, the differential 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. If the
differential data still exists after the 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 fewer for
updating I/O.
When the volumes are fully synchronized (that is, when there is no differential data on the 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. XP 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.
Figure 6 Data Flow during a Volume Migration Operation
Overview of Volume Migration
11