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Chapter 2 Data Replication
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2
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2
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6
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R
R
R
V
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In the Replicate state and Restore state, MV is synchronized with RV to always match the volume data
between MV and RV. Since the difference between MV and RV is reflected in the disk array
independently of the operating system or file system, however, the volume of RV may become
inconsistent. Therefore, the data replication function cannot impose access restrictions for MV, and
MV can be referred to and updated at any time. The function can impose access restrictions for RV
for activity state to prevent malfunction.
Table 2-4 shows the states which can be specified as RV access restrictions.
Table 2-4 RV Access Restriction
Activity State
Access Restriction Description
rpl rst sep/exec separated
Read/Write (R/W) RV is enabled for read/write.
- -
∆
Note 1
{
Read Only (RO) RV is enabled only for reading.
∆
Note 2
∆
Note 2
∆
Note 2
∆
Note 3
Not Ready (NR) RV is disabled for read/write.
{ { {
-
Not Available (NA)
RV is not recognized by the
operating system or the LU
(Logical Unit) is invalid.
∆
Note 4
∆
Note 4
∆
Note 4
∆
Note 4
{: Available ∆: Available with administrative restrictions -: Unavailable
rpl: Replicate state RW: Read/Write
rst: Restore state RO: Read Only
sep/exec: Separate execution NR: Not Ready
separated: Separated state NA: Not Available
Note 1: For Separate(immediate), “Read/Write (RW)” is set even during execution of Separate.
However, keep the following operational influence in mind:
1. Data is being copied from the MV into RV during Separate execution. Therefore, if the
I/O load on the RV is high, I/O performance on the MV side may lower.
Note 2: You can set “Read Only (RO)” to RV in the Replicate state, Restore state, or Separate
execution. In this case, note the following.
1. No update to MV should be done when RV is referred to in the Replicate state or Restore
state.
2. For updates to MV, I/O processing is done to the disk by the operating system control of
the file system. Even if the application has completed the update process to the disk, it
has not necessarily completed the update process to MV. Reflection of the update to RV
is processed in the disk array independent of the operating system.
Therefore, RV cannot be referred to normally because it is not consistent as a volume.
You can use it if consistency is assured in the specific operation.