Motorola 6806800C08B 사용자 설명서
Checkpoint Service
NetPlane Core Services
NetPlane Core Services Overview User’s Guide (6806800C08B)
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In the case of asynchronous update option, one of the replicas is designated as the active
replica. Data is always read from the active replica and there is no guarantee that all the other
replicas contain identical data. A write call returns after updating the active replica.
replica. Data is always read from the active replica and there is no guarantee that all the other
replicas contain identical data. A write call returns after updating the active replica.
In the case of synchronous update options, the call invoked to write to the replicas returns only
when all replicas have been updated, i.e. either all replicas are updated or the call fails and no
changes are made to the replicas.
when all replicas have been updated, i.e. either all replicas are updated or the call fails and no
changes are made to the replicas.
The CPSv supports both collocated and non-collocated checkpoints. In case of checkpoints
opened with collocated and asynchronous update option, it is up to the application to set a
checkpoint to the active state. In all other cases the CPSv itself handles which checkpoint is
currently active.
opened with collocated and asynchronous update option, it is up to the application to set a
checkpoint to the active state. In all other cases the CPSv itself handles which checkpoint is
currently active.
The Checkpoint Service defined by SAF does not support hot-standby. This means that the
currently stand-by component is not notified of any changes made to the checkpoint. When the
stand-by component gets active, it has to iterate through the respective checkpoint sections to
get up-to-date. To overcome this drawback, the CPSv provides additional, non-SAF APIs which
help to notify the stand-by component of changes and thus facilitate the implementation of a
hot-stand-by.
currently stand-by component is not notified of any changes made to the checkpoint. When the
stand-by component gets active, it has to iterate through the respective checkpoint sections to
get up-to-date. To overcome this drawback, the CPSv provides additional, non-SAF APIs which
help to notify the stand-by component of changes and thus facilitate the implementation of a
hot-stand-by.
2.5.2.2
Architecture
The CPSv service consists of the following subparts:
z
Checkpoint Director (CPD)
z
Checkpoint Node Director (CPND)
z
Checkpoint Agent (CPA)
2.5.2.2.1
Checkpoint Director
The Checkpoint Director runs on the active system manager node. Its main tasks are:
z
Generating a unique ID for each new checkpoint created by applications
z
Maintaining the list of nodes on which replicas of a particular checkpoint exist
z
Selecting the Checkpoint Node Director (CPND) which oversees the active replica for each
checkpoint
checkpoint
z
Coordinating the creation and deletion of checkpoints
z
Maintaining a repository for the CPSv policy and configuration-related information
There is an active and a stand-by CPD running respectively on the two system manager nodes.
CPD uses the NCS Message based Checkpoint Service to keep the two synchronized and
available for failover situations.
CPD uses the NCS Message based Checkpoint Service to keep the two synchronized and
available for failover situations.