Management of the status for global-active device pairs
Global-active device pairs are managed based on the following statuses and mode:
- GAD status
Status of a global-active device pair. The value is determined by the combination of the pair status and I/O mode, and is not output anywhere.
- Pair status
Pair statuses for the primary volume and the secondary volume
- I/O mode
I/O modes for the primary volume and the secondary volume
The following table shows GAD status values.
|
GAD status |
Description |
|
|---|---|---|
|
Simplex |
Status before creating a pair |
|
|
Mirroring |
The status is being changed to the mirrored status. This status indicates either of the following cases:
|
|
|
Mirrored |
The pair is running normally. Data is duplicated. |
|
|
Suspended |
The pair is suspended by operation or due to a failure. The latest data is stored in either the P-VOL or the S-VOL. I/O from the host targets only the volume that contains the latest data. |
|
|
Blocked |
Multiple failures occurred at the same time, and neither the P-VOL nor the S-VOL accepts I/O from the host. This status indicates either of the following cases:
|
|
The following table shows pair status values. The primary volume and the secondary volume each have the pair status.
|
Pair status |
Description |
|---|---|
|
SMPL |
Unpaired volumes |
|
COPY |
A pair is being created. An initial copy or resynchronization is being performed. |
|
PAIR |
Paired volumes The initial copy is completed, and data is duplicated. |
|
PSUS |
The pair is suspended by operation. (This value is output for the P-VOL.) |
|
SSUS |
The pair is suspended by operation, and the S-VOL is not updated. (This value is output for the S-VOL.) |
|
PSUE |
The pair is suspended and blocked due to a failure. |
|
SSWS |
The pair is suspended by operation or due to a failure, and the P-VOL is not updated. (This value is output for the S-VOL.) |
The following table shows I/O mode values. I/O mode indicates the I/O operations for the primary and secondary volumes that make up a global-active device pair.
|
I/O mode |
Status |
Read processing |
Write processing |
|---|---|---|---|
|
L/M |
Mirror (RL) |
Data in the volume on the local storage system is sent to the host. |
Data is written to the volumes on the local storage system and the remote storage system, in this order. |
|
L/L |
Local |
Data in the volume on the local storage system is sent to the host. |
Data is written to the volume on the local storage system only. |
|
B/B |
Block |
Denied. (An illegal request is returned.) |
Denied. (An illegal request is returned.) |
"L" indicates "local". "M" indicates "Mirror". "B" indicates "Block".
The following table shows the relationships of the GAD status, pair status, and I/O mode.
|
GAD status |
Trigger of suspension |
P-VOL |
S-VOL |
Volume that contains the latest data |
||
|---|---|---|---|---|---|---|
|
Pair status |
I/O mode |
Pair status |
I/O mode |
|||
|
Simplex |
-- |
SMPL |
-- |
SMPL |
-- |
-- |
|
Mirroring |
-- |
COPY |
L/M |
COPY |
B/B |
P-VOL |
|
Mirrored |
-- |
PAIR |
L/M |
PAIR |
L/M |
P-VOL S-VOL |
|
Suspended (P-LOCAL) |
Operation for the pair |
PSUS |
L/L |
SSUS |
B/B |
P-VOL |
|
Failure |
PSUE |
L/L |
PSUE |
B/B |
||
|
SMPL |
-- |
|||||
|
N |
N |
|||||
|
Suspended (S-LOCAL) |
Operation for the pair |
PSUS |
B/B |
SSWS |
L/L |
S-VOL |
|
Failure |
PSUE |
B/B |
SSWS |
L/L |
||
|
SMPL |
-- |
|||||
|
N |
N |
|||||
|
Blocked |
-- |
PSUE |
B/B |
PSUE |
B/B |
P-VOL S-VOL |
|
N |
N |
|||||
|
N |
N |
PSUE |
B/B |
|||
(Legend)
--: Not applied.
N: The I/O mode and pair status cannot be confirmed due to a storage system failure.
In the following cases, if you perform an operation on a pair, the request successfully returns a response, but the details specified in the request body are not actually applied:
- When you perform a pair suspending operation on a pair for which the status is PSUS or SSUS
- When you perform a pair resynchronization operation on a pair for which the status is COPY or PAIR