There are three types of Just Resynchronization Mechanism (JRM): for volumes, for slices and for proxies.
JRM for Volumes
JRM for volumes speeds up the resynchronization process when booting the system after a system panic or the like. GDS records the changed portion in the private slice. The resynchronization copy performed at rebooting after an unexpected system failure copies the only portion that was written during the system down to realize high-speed resynchronization and minimize the load of copy processing.
See
For details on the setting methods, see "5.2.3.4 Volume Configuration" and "D.4 sdxvolume - Volume operations."
For details on the changing methods, see "5.4.3 Volume Configuration" and "D.7 sdxattr - Set objects attributes."
When using GDS Management View, the mode ("on" or "off") of JRM for volumes can be checked using the volume information field in the Main Screen. For details, see "5.3.1.1 Confirming SDX Object Configuration."
When using a command, the mode of JRM for volumes can be checked using the JRM field of the volume information displayed with the sdxinfo command. For details, see "D.6 sdxinfo - Display object configuration and status information."
Note
Under the following circumstances, normal resynchronization is performed even though the JRM mode of the volume is on:
There is any slice in status other than ACTIVE or STOP, and a system panic occurs.
If the proxy is joined, this condition is also applied to the status of the proxy slice.
JRM for Slices
JRM for slices speeds up the resynchronization process when reattaching a detached slice to the volume. GDS records the changes made on the volume and slice in the memory while the slice is being detached. The resynchronization copy performed when the detached slice is reattached copies the updated portions only to realize high-speed resynchronization.
JRM for slices becomes effective when a slice is detached while the jrm attribute of the slices is on. However, if a system is stopped or if the slice is taken over by the sdxslice -T command while the slice is detached, just resynchronization is not conducted when the temporarily detached slice is attached again. Resynchronization is performed by copying the entire data, not only the updated portions.
Therefore, if you plan to shut down the system, or have a slice taken over, attaching the slice to the volume in advance is highly recommended.
See
For details on the setting methods, see "D.5 sdxslice - Slice operations."
For details on the changing methods, see "D.7 sdxattr - Set objects attributes."
The mode of JRM for slices can be checked using the JRM field of the slice information displayed with the sdxinfo command with the -e long option. For details, see "D.6 sdxinfo - Display object configuration and status information."
JRM for Proxies
JRM for proxies speeds up the just resynchronization process when joining a parted proxy again to the master and when the master data is restored from the proxy. GDS records the changes made on the master and the proxy on the memory while the proxy is parted. The just resynchronization conducted when rejoining or restoring copies only the updated portions to realize high-speed synchronization.
JRM for proxies is enabled when the pjrm attribute of a proxy volume is set to "on" and the proxy volume is parted. However, if any node that is included in the scope of the class is stopped while the proxy is parted, just resynchronization is not put in operation. In other words, the entire data, not only the updated portions, is copied.
Therefore, if you plan to shut down the system, joining the proxy to the master in advance is highly recommended.
Reference to these matters is not necessary when you are using the copy function of a disk unit.
See
For details on the setting methods, see "5.3.2.2 Backup (by Synchronization)" and "D.14 sdxproxy - Proxy object operations."
For details on the changing methods, see "D.7 sdxattr - Set objects attributes."
When using GDS Management View, the mode ("on" or "off") of JRM for proxies can be checked using the proxy volume information field in the Main Screen. For details, see "5.3.1.2 Viewing Proxy Object Configurations."
When using a command, the mode of JRM for proxies can be checked using the PJRM field of the volume information displayed with the sdxinfo command with the -e long option. For details, see "D.6 sdxinfo - Display object configuration and status information."
