V-Vols Number Of Snapshot; Cascade Restrictions With Snapshot V-Vol - Hitachi AMS2100 User Manual

Table 1-4: Read/Write Instructions to SnapShot P-VOL on the
TrueCopy S-VOL
Synchronizing
Split
NOTE: Failure in this table excludes a condition in which access of an LU
is not allowed (for example, LU blockage).

V-VOLs number of SnapShot

Cascade restrictions with SnapShot V-VOL

1-14
Hitachi AMS 2000 Family Copy-on-Write SnapShot User Guide
•
Remote Side (TrueCopy)
Paired
+, R
Paired
+, R
+, R/W
R/W
+, R
R
+, R
Failure
+ indicates a possible case, – indicates an impossible case
∆
indicates a case where a pair operation causes an error (a case that
can occur as a result of a change of the pair status to Failure)
R/W: Read/Write by a host is possible.
R: Read by a host is possible but write is impossible.
W: Write by a host is possible but read is impossible.
R/W: Read/Write by a host is impossible.
•
V-VOLs of up to 32 generations can be made even in the case where
the SnapShot P-VOL is cascaded with the P-VOL and S-VOL of
TrueCopy in the same way as in the case where no cascade
connection is made.
The following explains the transition of statuses of TrueCopy and
SnapShot pairs
About cascading of an LU of TrueCopy with a SnapShot V-VOL, it is
supported only when the SnapShot V-VOL and a TrueCopy P-VOL are
the same LU. Besides, operations of the SnapShot and TrueCopy
pairs are restricted depending on statuses of the pairs.
When cascading volumes of TrueCopy with a SnapShot V-VOL, create
a SnapShot pair first. When a TrueCopy pair is created earlier, split
the TrueCopy pair once and create a pair using SnapShot.
SnapShot overview
SnapShot P-VOL
Synchronizing Split
(Restore)
–
+, R
–
+, R
+, R/W +, R/W
–
+, R
–
+, R
Failure
Failure
(Restore)
–
+, R
–
+, R
∆
+, R/W , R/W
–
+, R
–
+, R