HP StorageWorks Continuous Access EVA Administrator Guide (T3687-96043, December 2005)

DR group log stat
es
ADRgrouplogcan
be in one of the following states:
• Unused (Normal)– No source virtual disk is logging or merging.
• Logging–At least one source virtual disk is writing to the DR group log but none are merging.
• Merging–At lea
st one source virtual disk is merging and logging.
DR group log size
When created, a log disk contains 139 MB of Vraid1 space. The log disk grows as needed when the DR
group is logging. The controller considers the log disk full when any of the following occurs:
• No free space remains in the disk group that contains the log disk.
• The log disk reaches 2 TB of Vraid1 (4 TB total).
• The log reaches the default or user-specified maximum log disk size (for the default maximum
log disk size, see the EVA replication soft ware release notes)
Full copy
When a DR g roup log is full, the controller deletes the log contents, returns all but 139 MB to the
disk group, and copies data in one–MB blocks directly from the source DR group's virtual disks to
the destination DR group's virtual disks. This method of synchronizing local and remote virtual disks
is called full copy. It is optimized to copy only blocks that were written after the remote connection
was lost.
Unlike a m erge, full copy does not provide crash consistency during the o peration. If the full
copy is no
t completed due to an event such as loss of the local array, the remote copy can be left in
an indeterminate state.
When logs are merging, you can use a replication interface to initiate a full copy of the source virtual
disk to the destination virtual disk ( except on arrays with VCS 3.x). Unlike the automatic full copy, the
interac
tive version copies all blocks from the source disk to the destination d is k. For information to
perform a full copy, see online help.
Managed sets
Managed sets are a feature of the replication mana ger. A managed set is a named collection of
resources b a n ded together for convenient managem ent. Performing an action on a managed set performs
the action on all members of the set. For example, the managed set Sales_Disks might include two
virtual disks, West_Sales and East_Sales. If you perform the New Snapshot action on the managed set
Sales_Disks, the interface creates a snapshot of West_Sales and a snapshot of East_Sales. A managed
set can contain DR groups, enabled hosts, host volumes, storage sy stems, or v irtual disks.
Here are a few facts about managed sets:
• All resources, or members, in a single managed set must be of the same type (for example,
all virtual disks).
• You can add a specific resource to more than one managed set.
• You can add resources on more than one array to a managed set.
• C reate sepa rate m anag ed sets for source and destination DR groups so that if a failover
occurs, you can p er form the actions that correspond to the changed source/destination role of
the managed set members.
Failover
Fai
lover in the context of replication is an operation that reverses replication direction. The destination
array assumes the role of the source and the source assumes the role of the destination. For example, if a
DR group is replicating from array A to array B, a failover would cause data to be replicated from array
B to array A. You can fail over DR groups and managed sets containing DR groups.
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