• Make sure that primary systems are configured to report sense
information to the host. Secondary systems should also be attached to a host server to enable reporting of sense information in the event of a problem with an S-VOL or secondary system. If the remote system is not attached to a host, it should be attached to a primary site host server so that monitoring can be performed.
• If power sequence control cables are used, set the power select switch for the cluster to LOCAL to prevent the primary system from being powered off by the host. Make sure the secondary system is not powered off during UR operations.
• Install the UR remote copy connections (cables, switches, and so on) between the primary and secondary systems.
• When setting up data paths, distribute them between different storage clusters and switches to provide maximum flexibility and availability. The logical paths between the primary and secondary systems must be separate from the logical paths between the host and secondary system.
System option modes
To provide greater flexibility, the Unified Storage VM has additional
operational parameters called system option modes (SOMs) that allow you to tailor the HUS VM to your unique operating requirements. The SOMs are set on the SVP by your Hitachi Data Systems representative.
The system option modes can be used for several kinds of UR customizations, including:
• 2DC configuration
• Delta resync configuration
• Configuring split options for mirrors
• Improving initial copy time
The following table describes SOMs for Universal Replicator. For a complete list of SOMs for the HUS VM, see the Hitachi Unified Storage VM Block Module Hardware User Guide.
Table 3-1 System option modes
Note: The SOM information may have changed since this document was published. Contact your Hitachi Data Systems representative for the latest SOM information.
Mode Description
448 When the SVP detects a blocked path:
Mode 448 ON: An error is assumed and the mirror is immediately suspended.
Mode 448 OFF: If the path does not recover within a specified period of time, an error is assumed and the mirror is suspended.
Note: Mode 448 setting is available only when mode 449 is set to OFF.
449 Mode 449 ON: The SVP does not detect blocked paths.
Mode 449 OFF: The SVP detects blocked paths and monitors the time until the mirrors are suspended.
466 It is strongly recommended that the path between the main and remote storage systems have a minimum data transfer speed of 100 Mbps. If the data transfer speed falls to 10 Mbps or lower, UR operations cannot be properly processed. As a result, many retries occur and UR pairs may be suspended. This SOM is provided to ensure proper system operation for data transfer speeds of at least 10 Mbps.
ON: Data transfer speeds of 10 Mbps and higher are supported.
The JNL read is performed with 4-multiplexed read size of 256 KB.
OFF (default): For conventional operations. Data transfer speeds of 100 Mbps and higher are supported. The JNL read is performed with 32-multiplexed read size of 1 MB by default.
Note: The data transfer speed can be changed using the Change JNL Group options.
474 With mode 474 set to ON, the initial copy time for a UR pair is improved when using the TC initial copy operation.
The procedure requires use of a script, with the following operations:
• UR initial copy operation, with "None" specified for the Initial Copy parameter.
• Split the UR pair.
• TC initial copy operation, using the split UR pair volumes.
• Delete the TC pair.
• Resynchronize the UR pair.
Mode 474 ON: Using CCI improves performance.
Mode 474 OFF: Operations run normally.
If the P-VOL and S-VOL are both DP-VOLs, initial copy
performance might not improve with SOM 474 set to ON. This is because with DP-VOLs, not all areas in a volume are allocated for UR; therefore not all areas in the P-VOL are copied to the S-VOL. With less than the full amount of data in the P-VOL being copied, the initial copy completes in a shorter time, which may not be improved with SOM 474.
Notes:
1. Set this mode for both MCU and RCU, otherwise the pair creation fails.
2. When this mode is set to ON:
-Execute all pair operations from CCI/Business Continuity Manager.
-Use a dedicated script.
-Version downgrade is disabled.
-Take Over is not available.
506 Enables the delta resync operation.
Mode 506 ON: The delta resync operation is performed if there are no update I/Os.
Mode 506 OFF: The copy processing of all data is performed if there is no update I/Os.
Mode Description
690 Controls whether to prevent Read JNL or JNL Restore when the Write Pending rate on RCU exceeds 60% as follows:
• When CLPR of JNL-Volume exceeds 60%, Read JNL is prevented.
• When CLPR of Data (secondary)-Volume exceeds 60%, JNL Restore is prevented.
MCU/RCU: This SOM applies to only the RCU.
Mode 690 ON: Read JNL or JNL Restore is prevented when the Write Pending rate on RCU exceeds 60%.
Mode 690 OFF (default): Read JNL or JNL Restore is not prevented when the Write Pending rate on RCU exceeds 60%
(the same as before).
Notes:
1. This SOM can be set online.
2. If the Write Pending status long keeps 60% or more on RCU, it takes extra time for the initial copy to be completed by making up for the prevented copy operation.
3. If the Write Pending status long keeps 60% or more on RCU, the pair status may become Suspend due to the JNL-VOL being full.
908 Changes cache memory (CM) capacity allocated to MPBs with different workloads.
Mode 908 ON: Difference in CM allocation capacity among MPBs with different workloads is large.
Mode 908 OFF (default): Difference in CM allocation capacity among MPBs with different workloads is small.
Notes:
1. Apply this SOM to CLPRs used only for UR JNLGs.
2. Since CM capacity allocated to MPBs with low workload is small, the performance is affected by a sudden increase in workload.
3. This SOM is effective for a CLPR. Therefore, when setting this SOM to ON/OFF, select target "LPRXX (XX=00 to 31)".
For example, even when CLPR0 is defined (CLPR1 to 31 are not defined), select "LPR00" first and then set the SOM to ON/OFF.
Mode Description