The local replica options provide additional settings to enable you to tailor your local replication environment to your specific operating requirements. The local replica options include the Copy Threshold option that your service representative can set and the options that you can set.
The local replica options apply to the following software applications:
- ShadowImage: options 1, 2, 9 to 13, 20 to 22, 24, 25, 26, 31
- ShadowImage for Mainframe: options 1, 2, 9 to 13, 20 to 22, 24, 25, 26, 31
- Thin Image Advanced: option 30
- Volume Migration: option 5
You can use CCI to view (raidcom get local_replica_opt) and manage (raidcom modify local_replica_opt) the local replica options for your storage system.
- Copy Threshold option
- The Copy Threshold option temporarily stops copy operations when the workload of the storage system is high to prevent degradation of host I/O performance. When this option is enabled, the following copy operations are stopped:
- ShadowImage
- ShadowImage for Mainframe
- Thin Image Advanced
- Volume Migration
- Compatible FlashCopy® V2
When you want to enable or disable the Copy Threshold option, contact your service representative.
- Other local replica options
- The following table lists and describes the local replica options for ShadowImage and ShadowImage for Mainframe.
Note the following when you use the Quick/Steady Split Multiplexing, Reverse Copy Multiplexing, or Normal Resync Multiplexing option:
- The increase in copy volume increases the amount of data to be written to the target volume.
- If the parity group performance is less than the pair split or resync performance, the amount of data waiting to be written to cache memory (cache write pending ratio) may increase until it exceeds 60%, and the copy processing might be placed in the wait state. In such a case, consider the copy order to reduce the number of pairs for which copy processing is executed concurrently for volumes provisioned by the same parity group.
- If the number of volumes to be resynchronized or split increases, the maximum number of jobs for pair split or resynchronization that can execute concurrently for a pair decreases. In this case, when you split or resynchronize many pairs concurrently with this option set, the pair split or resynchronization performance might not be changed.
- The maximum number of ShadowImage for Mainframe copy operations that can be run concurrently is 126 for VSP One Block 20 series and 253 for VSP One Block 85, including ShadowImage, ShadowImage for Mainframe, and Volume Migration. This number includes initial copying, resynchronization, update copying, and differential data copying. When copy operations other than pair split and resynchronization are running concurrently, if you set this option, the pair split or resynchronization performance might not be changed.
- The maximum number of pairs that can be copied concurrently in the background is 504. If the number of pairs being copied reaches 504, the next pair to be copied waits until one of the copy processing finishes.
- The Quick/Steady Split Multiplexing option is enabled for Steady Split and Quick Split.
- Reverse Copy Multiplexing is enabled for Reverse Copy.
- Normal Resync Multiplexing is enabled for Normal Resync.
- If the Increase Background Copy Performance option is enabled, the amount of copy data increases over the entire storage system while the pair is in the PAIR/DUPLEX status. Therefore, you can decrease the amount of differential data when the pair-split operation starts. However, the MP operating ratio and cache write pending rate increase because the amount of copy data increases in the storage system. Understand the trade-offs when you use this option.
- The Host I/O Performance option reduces the impact on host I/O by lowering the copy activity when pairs are in the CPPD/PENDING, PAIR/DUPLEX, COPY/TRANS, PSUP/SUSPVS, CPRS/PENDING, or RCPY/REVRSY status.
- The Copy Pace Ext. options reduce the impact on host I/O by lowering the copy activity when pairs are in the PAIR/DUPLEX status.
These options can be set concurrently. If you set both options, you can benefit from both.
|
No. |
Default |
Option |
Description |
|---|---|---|---|
|
1 |
OFF |
Swap & Freeze |
Suppresses update copy operations after you create a pair. Suppressing update copy operations reduces the impact on host I/O performance but keeps the P-VOL and S-VOL unsynchronized. You can also use this option to suppress update copy operations after Quick Restore and save the SIz data as-is immediately after Quick Restore. After Quick Restore, the paired S-VOL in PAIR/DUPLEX status is not updated and remains unchanged. |
|
2 |
OFF |
Host I/O Performance |
Gives higher priority to host I/O responses than copy processing. This option improves host I/O responses by controlling SIz copy operations. When you enable this option, copy operations are suppressed regardless of host I/O workload. (VSP One B85) If an SIz pair exists, host I/O responses might not improve even if this option is enabled for SI. If so, enable this option for SIz as well. |
|
5 |
OFF |
(VSP One B85) Compatible Multiplicity Mode |
This option reduces the maximum multiplicity of copy processing (maximum number of jobs allowed for concurrent copy processing) by ShadowImage and Volume Migration for each storage system from 253 to 126. The maximum multiplicity for each pair and the maximum multiplicity for asynchronous copy processing in PAIR/DUPLEX status differ depending on the combination of the settings of this option and the following local replica options. For details, see the following table (below).
|
|
9 10 11 12 13 |
OFF |
Host I/O Priority Mode settings: Host I/O Priority Mode 1 Host I/O Priority Mode 2 Host I/O Priority Mode 3 Host I/O Priority Mode 4 Host I/O Priority Mode 5 (ShadowImage, ShadowImage for Mainframe) |
Makes the copy processing for SIz pairs fail after a specified time so that host I/O is prioritized. This function is performed if the cache write pending rate does not decrease and the host I/O does not finish within the time period that you specify. After copy processing fails, all differential data is copied using a resynchronization operation. For details about specifying the time until copy processing fails, see Time until the copy processing fails. |
|
20 21 22 |
OFF |
Copy Pace Ext.2 settings: Copy Pace Ext. Slower1 Copy Pace Ext. Slower2 Copy Pace Ext. None |
Improves host I/O performance by controlling the pace at which copy operations are performed for SIz pairs in the PAIR/DUPLEX status. This option is enabled for all SIz pairs in the PAIR/DUPLEX status.
Copy Pace Ext. None takes precedence over Copy Pace Ext. Slower2, and Copy Pace Ext. Slower2 takes precedence over Copy Pace Ext. Slower1. This function is applied only to pairs in the PAIR/DUPLEX status. This function is not applied to pairs in the CPPD/PENDING, COPY/TRANS, PSUP/SUSPVS, CPRS/PENDING, or RCPY/REVRSY status. Note: When the Copy Pace Ext. None option is set, copy operations are not performed for pairs in the PAIR/DUPLEX status and the synchronization rate during split operations might become lower. In this case, a pair might remain in PSUP/SUSPVS or COPY/TRANS status during a split operation for a longer time. If this is a problem, perform either or both of the following actions:
|
|
24 |
ON |
Quick/Steady Split Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Accelerates SI pair split. (VSP One B85) The maximum multiplicity of copy processing (maximum number of jobs allowed for concurrent copy processing) for each pair changes depending on the combination of the setting of this option and the setting of the Compatible Multiplicity Mode option. For details, see the following table (below). |
|
25 |
ON |
Reverse Copy Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Accelerates SI reverse resynchronization (S-VOL to P-VOL). (VSP One Block 85) The maximum multiplicity of copy processing (maximum number of jobs allowed for concurrent copy processing) for each pair changes depending on the combination of the setting of this option and the setting of the Compatible Multiplicity Mode option. For details, see the following table (below). |
|
26 |
ON |
Normal Resync Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Accelerates SI forward resynchronization (P-VOL to S-VOL). (VSP One Block 85) The maximum multiplicity of copy processing (maximum number of jobs allowed for concurrent copy processing) for each pair changes depending on the combination of the setting of this option and the setting of the Compatible Multiplicity Mode option. For details, see the following table (below). |
|
31 |
OFF |
Increase Background Copy Performance (ShadowImage, ShadowImage for Mainframe) |
(VSP One B85) The combination of the setting of this option and the setting of the Compatible Multiplicity Mode option changes the maximum multiplicity of asynchronous copy processing (maximum number of jobs allowed for concurrent copy processing) run in the background when a ShadowImage pair is in PAIR status. For details, see the following table (below). |
No. 24 (VSP One Block 85)
|
Option settings |
Maximum multiplicity for each pair |
|
|---|---|---|
|
Quick/Steady Split Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Compatible Multiplicity Mode |
|
|
ON |
ON |
24 |
|
OFF |
48 |
|
|
OFF |
ON |
1 |
|
OFF |
1 |
|
No. 25 (VSP One Block 85)
|
Option settings |
Maximum multiplicity for each pair |
|
|---|---|---|
|
Reverse Copy Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Compatible Multiplicity Mode |
|
|
ON |
ON |
24 |
|
OFF |
48 |
|
|
OFF |
ON |
1 |
|
OFF |
1 |
|
No. 26 (VSP One Block 85)
|
Option settings |
Maximum multiplicity for each pair |
|
|---|---|---|
|
Normal Resync Multiplexing (ShadowImage, ShadowImage for Mainframe) |
Compatible Multiplicity Mode |
|
|
ON |
ON |
24 |
|
OFF |
48 |
|
|
OFF |
ON |
1 |
|
OFF |
1 |
|
No. 31 (VSP One Block 85)
|
Option settings |
Maximum multiplicity |
|
|---|---|---|
|
Increase Background Copy Performance (ShadowImage, ShadowImage for Mainframe) |
Compatible Multiplicity Mode |
|
|
ON |
ON |
126 |
|
OFF |
253 |
|
|
OFF |
ON |
64 |
|
OFF |
126 |
|