REC Data Transfer Mode Comparison

This section describes the REC data transfer mode.

Table: REC Data Transfer Mode (1/2)

Data transfer mode

Typical application

Effects on the response to Write I/Os from the server

During the initial copy

After the initial copy is completed

Synchronous transfer mode

  • Data mirroring between ETERNUS DX/AF storage systems within a site

  • Backup to other ETERNUS DX/AF storage systems within a site

Typically, system response is slightly affected. In order to maintain a balance between the copy process and the update process from Write I/Os, there may be cases of a delayed Write I/O response.

System response is always affected.

Asynchronous transfer mode

Stack mode

Remote backup

System response is slightly affected.

System response is slightly affected.

Consistency mode

Remote mirroring

Typically, system response is slightly affected. In order to maintain a balance between the copy process and the update process from Write I/Os, there may be cases of a delayed Write I/O response.

Typically, system response is slightly affected, but if the data transfer path is too narrow, the response deteriorates. Furthermore, when an excessive response delay occurs, copying is suspended to prevent further response delays.

Through mode

This mode is temporarily enabled when the Stack mode/Consistency mode is disabled or when the sessions are suspended.

Typically, system response is slightly affected. In order to maintain a balance between the copy process and the update process from Write I/Os, there may be cases of a delayed Write I/O response.
Table: REC Data Transfer Mode (2/2)

Data transfer mode

Data status in the event of a disaster

Guaranteed order property

Transition to equivalent state

Synchronous transfer mode

Copy source and copy destination are always identical.

Yes

Yes

Asynchronous transfer mode

Stack mode

Some copy source writes may not have been propagated to the copy destination yet.

No

No

Consistency mode

Yes

Yes

Through mode

No

Yes