Operation When A Split Command Is Issued During I/O Processing (For Truecopy); Operation When An I/O Request Is Received While A Split Command Is In Progress; Host Access After Split - Hitachi G200 User Manual

In this case, resynchronize the consistency group, and then run the split
command again.

Operation when a split command is issued during I/O processing (for TrueCopy)

The figure below explains how data consistency between secondary volumes
of pairs in a group is maintained when a split command is issued during I/O
processing.
In TrueCopy, if an I/O request is being processed in a volume when the
pairsplit -r command is issued to a consistency group, the volume is split
after the I/O processing and data transfer to the secondary volume are
completed. Data consistency can be maintained through this operation, as
shown in the following figure.

Operation when an I/O request is received while a split command is in progress

When a pair in a consistency group in which a split command is in progress
receives an I/O request from a server, if the applicable pair is not split yet, it
is split first. The I/O request is accepted after the pair is split. The same
operation is performed if a pair in a group is split due to a failure. As a result,
data consistency between secondary volumes in a group can be maintained.

Host access after split

You can specify settings for read/write access to the P-VOL/P-VOL and S-
VOL/S-VOL in consistency groups after pairs are split. These settings are
specified using CCI.
For TC volumes, read access cannot be prohibited regardless of specified
options. For details about each option, see the Command Control Interface
User and Reference Guide and the Command Control Interface Command
Reference.
• The CCI settings for TC are optional.
The following tables show the effects of the settings on read and write access.
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Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
Planning for TrueCopy