HP P2000 HP P2000 G3 MSA System SMU Reference Guide - Page 110

Performing initial replication locally or remotely, must be resumed manually.

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The figure above illustrates initial, delta, and queued replications: • Initial replication: When the first replication is initiated, a snapshot of the primary volume is taken and every block of data is then copied to the secondary volume. When the copy is complete, the first snapshot is taken on the secondary volume, creating the first sync point. This sync point can be used to determine the delta data from that sync point to a later snapshot. Actions 1-4 are the initial replication. • Delta replications: Delta data is the "list" of 64-KB blocks that differs between the last snapshot replicated and the next snapshot to be replicated. This delta data is then replicated from the replication snapshot on the primary volume to the secondary volume. Once the initial replication has completed, all future replications for that replication set will be delta replications so long as sync points are maintained. Action 5 is a delta replication. • Queued replications: New replications can be initiated while other replication snapshots are in the process of being replicated. This enables you to take snapshots at specific intervals while other replications are ongoing. Note that a replication that is initiated while another to the same secondary volume is ongoing will be queued, and will not begin to transfer data until the prior one completes. In action 3, Snap 2 is queued while Snap 1 is being replicated; in action 7, Snap 3 is queued while Snap 2 is being replicated. An in-progress replication can be suspended, either manually by a user or automatically if a network error occurs. If you want the replication to continue, you must manually resume it; or, if you want to cancel the replication, you can abort it. IMPORTANT: For a replication to begin, the controller that owns the secondary volume must have a link to the controller that owns the primary volume. This link must be of the type specified by the link-type parameter supplied during replication set creation or modification. If all links to the controller that owns the primary volume fail, but links remain between its partner controller and the controller that owns the secondary volume, replications currently in progress or queued may continue, but their progress may not be reported correctly; replications requested after the links fail will not start replicating. If the controller that owns the secondary volume loses all links to both controllers of the primary system, then the replications will suspend and progress will be updated appropriately; links from the partner controller of the controller that owns the secondary volumes are not considered for use. Replications that enter the suspended state must be resumed manually. Performing initial replication locally or remotely When you set up replication for a volume, you specify to use a secondary volume in a vdisk in either the local (primary) system or a remote (secondary) system. • If the speed of the initial replication is most important, specify a vdisk that is owned by the same controller as the primary volume's vdisk in the local system. After replication is set up, you can perform the initial replication and then physically move the vdisk containing the secondary volume and its snap pool into a remote system. Moving a vdisk involves using SMU to detach the secondary volume and stop its vdisk, removing the vdisk's disks or enclosure, transporting the disks or enclosure to the remote location, inserting the disks or enclosure into the remote system, and using SMU to restart the vdisk and reattach the secondary volume. If the secondary volume's snap pool is in a different vdisk then that vdisk must also be stopped, moved, and restarted. • If ease of setup is most important, specify a vdisk owned by either controller in a remote system. After replication is set up, you can start replication. In either case, you must specify whether FC or iSCSI links will be used for replication between the primary and secondary systems and you cannot change this setting for the life of the replication set. 110 Using Remote Snap to replicate volumes

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110
Using Remote Snap to replicate volumes
The figure above illustrates initial, delta, and queued replications:
•
Initial replication: When the first replication is initiated, a snapshot of the primary volume is taken and
every block of data is then copied to the secondary volume. When the copy is complete, the first
snapshot is taken on the secondary volume, creating the first sync point. This sync point can be used to
determine the delta data from that sync point to a later snapshot. Actions 1–4 are the initial replication.
•
Delta replications: Delta data is the “list” of 64-KB blocks that differs between the last snapshot
replicated and the next snapshot to be replicated. This delta data is then replicated from the replication
snapshot on the primary volume to the secondary volume. Once the initial replication has completed,
all future replications for that replication set will be delta replications so long as sync points are
maintained. Action 5 is a delta replication.
•
Queued replications: New replications can be initiated while other replication snapshots are in the
process of being replicated.
This enables you to take snapshots at specific intervals while other
replications are ongoing.
Note that a replication that is initiated while another to the same secondary
volume is ongoing will be queued, and will not begin to transfer data until the prior one completes. In
action 3, Snap 2 is queued while Snap 1 is being replicated; in action 7, Snap 3 is queued while Snap
2 is being replicated.
An in-progress replication can be suspended, either manually by a user or automatically if a network error
occurs. If you want the replication to continue, you must manually resume it; or, if you want to cancel the
replication, you can abort it.
IMPORTANT:
For a replication to begin, the controller that owns the secondary volume must have a link to
the controller that owns the primary volume. This link must be of the type specified by the link-type
parameter supplied during replication set creation or modification. If all links to the controller that owns the
primary volume fail, but links remain between its partner controller and the controller that owns the
secondary volume, replications currently in progress or queued may continue, but their progress may not
be reported correctly; replications requested after the links fail will not start replicating. If the controller that
owns the secondary volume loses all links to both controllers of the primary system, then the replications
will suspend and progress will be updated appropriately; links from the partner controller of the controller
that owns the secondary volumes are not considered for use. Replications that enter the suspended state
must be resumed manually.
Performing initial replication locally or remotely
When you set up replication for a volume, you specify to use a secondary volume in a vdisk in either the
local (primary) system or a remote (secondary) system.
•
If the speed of the initial replication is most important, specify a vdisk that is owned by the same
controller as the primary volume’s vdisk in the local system.
After replication is set up, you can perform the initial replication and then physically move the vdisk
containing the secondary volume and its snap pool into a remote system. Moving a vdisk involves using
SMU to detach the secondary volume and stop its vdisk, removing the vdisk’s disks or enclosure,
transporting the disks or enclosure to the remote location, inserting the disks or enclosure into the
remote system, and using SMU to restart the vdisk and reattach the secondary volume. If the secondary
volume’s snap pool is in a different vdisk then that vdisk must also be stopped, moved, and restarted.
•
If ease of setup is most important, specify a vdisk owned by either controller in a remote system. After
replication is set up, you can start replication.
In either case, you must specify whether FC or iSCSI links will be used for replication between the primary
and secondary systems and you cannot change this setting for the life of the replication set.