HP P6000 Continuous Access Implementation Guide (T3680-96431, August 2012)

NOTE: Managed sets are simply a feature that enables you to manage multiple resources easily.
They do not contribute to the data consistency of a DR group. Write order consistency is maintained
at the DR group level.
In 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.
• You should create separate managed sets for DR groups so that if a failover occurs, you can
perform the actions that correspond to the changed source/destination role of the managed
set members.
Failover
In HP P6000 Continuous Access replication, failover reverses replication direction for a DR group.
The destination array assumes the role of the source, and the source array assumes the role of the
destination. For example, if a DR group on array A is replicating to array B, a failover would cause
data for the DR group to be replicated from array B to array A.
You can failover a single DR group or you can failover multiple DR groups with a single command
using a managed set. When you specify a failover action for a specific managed set, the failover
occurs for all DR groups contained in the specified managed set. Without managed sets, you must
fail over each DR group individually. For more information on failover settings, see “Creating and
presenting source virtual disks” (page 96).
NOTE: Failover can take other forms:
• Controller failover—The process that occurs when one controller in a pair assumes the workload
of a failed or redirected controller in the same array.
• Fabric or path failover—I/O operations transfer from one fabric or path to another.
This guide describes the failover of DR groups and managed sets. It does not address controller
failover within a cabinet, or path, or fabric failover, because redundancy is assumed.
Failsafe mode
Failsafe mode is only available when a DR group is being replicated in synchronous mode and
specifies how host I/O is handled if data cannot be replicated between the source and destination
array. The failsafe mode can be on of the following:
• Failsafe enabled—All host I/O to the DR group is stopped if data cannot be replicated between
the source array and destination array. This ensures that both arrays will always contain the
same data (RPO of zero). A failsafe-enabled DR group can be in one of two states:
◦ Locked (failsafe-locked)—Host I/O and remote replication have stopped because data
cannot be replicated between the source and destination array.
◦ Unlocked (failsafe-unlocked)—Host I/O and remote replication have resumed once
replication between the arrays is re-established.
• Failsafe disabled—If replication of data between the source and destination array is interrupted,
the host continues writes to the source array, but all remote replication to the destination array
stops and I/Os are put into the DR group write history log until remote replication is
re-established.
10 HP P6000 Continuous Access