Cascading Snapshot With Truecopy Extended Distance - Hitachi AMS2100 User Manual

Cascading SnapShot with TrueCopy Extended Distance

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Hitachi AMS 2000 Family Copy-on-Write SnapShot User Guide
The SnapShot P-VOL can be cascaded (shared) with both the primary
and secondary TrueCopy Extended Distance (TCE) volumes, as
shown in Figure 2-9. A V-VOL cannot be cascaded.
•
Figure 2-9: Basic SnapShot Cascade Examples with TrueCopy
The TCE pair can be cascaded only with the SnapShot P-VOL, but the
following restriction is placed on the cascade connection.
• The restoration of the SnapShot pair cascaded with the TCE P-
VOL can be done only when the status of the TCE pair is
Simplex, Split, or Pool Full.
• When restoring the SnapShot pair cascaded with the TCE S-VOL,
it is required to make the status of the TCE pair Simplex or Split.
The restoration can be done in the Takeover status, but it cannot
be done when the status is Busy in which the S-VOL is being
restored using the data pool data.
• When the TCE S-VOL is in the Busy status in which it is being
restored using the data pool data, the Read/Write instruction
cannot be issued to the SnapShot V-VOL cascaded with the TCE
S-VOL.
SnapShot requires restart to store the resource for the data pool
management in the cache memory at the time of installation. This
resource, however, is common to the resource for the data pool
management of TCE. Therefore, when using SnapShot and TCE
together, restart it only once when either one is installed first.
V-VOLs of up to 32 generations can be made even in the case where
the P-VOL of SnapShot is cascaded with the P-VOL and S-VOL of TCE
in the same way as in the case where no cascade connection is made.
Planning and design
Extended