SRDF view
The SRDF view is composed of the SRDF state and internal SRDF device state. These
states indicate whether the device is available to send data across the SRDF links, and
able to receive software commands.
R1 device states
An R1 device can have the following states for SRDF operations:
l
Ready—The R1 device is ready for SRDF operations.
The R1 device is able to send data across the SRDF links.
True even if local mirror(s) of the R1 device are Not Ready for I/O operations.
l
Not Ready (SRDF mirror Not Ready)—The R1 device is Not Ready for SRDF
operations.
When the R2 device is placed into a Read/Write state to the host, the corresponding
R1 device is automatically placed into the SRDF mirror Not Ready state.
R2 device states
An R2 device can have the following states for SRDF operations:
l
Ready—The R2 device receives the updates propagated across the SRDF links
and can accept SRDF host-based software commands.
l
Not Ready—The R2 device cannot accept SRDF host-based software commands,
but can still receive updates propagated from the primary array.
l
Link blocked (LnkBlk) — Applicable only to R2 SRDF mirrors that belong to R22
devices.
One of the R2 SRDF mirrors cannot receive writes from its associated R1 device.
In normal operations, one of the R2 SRDF mirrors of the R22 device is in this state.
R1/R2 device accessibility
Accessibility of a SRDF device to the host depends on both the host and the array
view of the SRDF device state.
Table 42 on page 121 and Table 43 on page 122 list host accessibility for R1 and R2
devices.
Table 42
R1 device accessibility
Host interface state SRDF state Accessibility
Read/Write Ready Read/Write
Not Ready Depends on R2 device availability
Read Only Ready Read Only
Not Ready Depends on R2 device availability
Not Ready Any Unavailable
Remote replication solutions
SRDF device states 121
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