HCP Tenant Management Help


System metadata collisions

A system metadata collision occurs when these events occur in the order shown:

1.Different changes are made to the system metadata for a given object on each of two systems in a replication topology.

2.The changed system metadata on one of the systems is replicated to the other system.

For example, suppose a user on one system changes the shred setting for an object while a user on the other system changes the index setting for the same object. When the object on either system is replicated to the other system, a system metadata collision occurs.

If a collision occurs when changed system metadata for a given object is replicated from one system (system A) in a replication topology to another system (system B) in the topology:

For changed system metadata other than the retention setting and hold status:

oIf the last change made on system A is more recent than the last change made on system B, HCP changes the system metadata on system B to match the system metadata on system A.

oIf the last change on system B is more recent than the last change on system A, HCP does not change the system metadata on system B.

For a changed retention setting:

oIf the retention setting on system A specifies a longer retention period than does the retention setting on system B, HCP changes the retention setting on system B to match the retention setting on system A.

oIf the retention setting on system B specifies a longer retention period than does the retention setting on system A, HCP does not change the retention setting on system B.

For a changed hold status:

oIf the object is on hold on system A but not on system B, HCP places the object on hold on system B.

oIf the object is on hold on system B but not on system A, HCP leaves the object on hold on system B.

Here are some examples of how HCP handles collisions when changed system metadata for a given object is replicated from one system (system A) in a replication topology to another system (system B) in the topology.

Example 1

The object starts out on both system A and system B with these system metadata settings:

Shred: false
Index: false

The table below shows a sequence of events in which the system metadata for the object is changed and the changes are then replicated.

Sequence

Event

1

On system A, a client changes the shred setting to true.

2

On system B, a client changes the index setting to true.

3

The changes on system A are replicated to system B. The resulting settings for the object on system B are:

Shred: false
Index: true

Example 2

The object starts out on both system A and system B with these system metadata settings:

Retention: Initial Unspecified
Shred: false
Index: false

The table below shows a sequence of events in which the system metadata for the object is changed and the changes are then replicated.

Sequence

Event

1

On system A, a client changes the retention setting to Deletion Prohibited.

2

On system B, a client changes the retention setting to Deletion Allowed.

3

On system B, a client changes the index setting to true.

4

On system A, a client changes the shred setting to true.

5

The changes on system A are replicated to system B. The resulting settings for the object on system B are:

Retention: Deletion Prohibited
Shred: true
Index: false

Example 3

The object starts out on both system A and system B with these system metadata settings:

Retention: Initial Unspecified
Hold: true
Shred: false
Index: false

The table below shows a sequence of events in which the system metadata for the object is changed and the changes are then replicated.

Sequence

Event

1

On system A, a client changes the retention setting to Deletion Allowed.

2

On system B, a client changes the retention setting to Deletion Prohibited.

3

On system B, a client changes the index setting to true.

4

On system A, a client changes the shred setting to true.

5

On system A, a client releases the object from hold.

6

The changes on system A are replicated to system B. The resulting settings for the object on system B are:

Retention: Deletion Prohibited
Hold: true
Shred: true
Index: false

7

The changes on system B are replicated to system A. The resulting settings for the object on system A are:

Retention: Deletion Prohibited
Hold: true
Shred: true
Index: false

© 2015, 2019 Hitachi Vantara Corporation. All rights reserved.