| PRIMECLUSTER Global Disk Services Configuration and Administration Guide 4.1 (Linux) |
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| Appendix A General Notes | > A.2 Important Points |
There are three types of Just Resynchronization Mechanism (JRM): for volumes, for slices and for proxies.
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.
When creating the volume in the Volume Configuration dialog box, set the JRM mode (to "on" or "off"). The default value is "on". For details, see "Volume Configuration."
When creating the volume with the sdxvolume -M command, specify the -a jrm={on off} option to set the JRM mode. By default, it is enabled. For details, see "sdxvolume - Volume operations."
For the methods for changing the mode ("on" or "off") of JRM for volumes, see "Volume Configuration."
To change the mode of JRM for volumes, specify the -a jrm={on off} option to the sdxattr -V command. For details, see "sdxattr - Set objects attributes."
For the mode ("on" or "off") of JRM for volumes, check the Volume Information Field in the Main Screen. For details, see "Confirming SDX Object Configuration."
For the mode of JRM for volumes, use the sdxinfo command and check the JRM field of the displayed volume information. For details, see "sdxinfo - Display object configuration and status information."
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.
When detaching the slice with the [Operation]:[Detach Slice] menu in the Main Screen, the JRM mode is set to "on". Setting the mode to "off" is impossible.
When detaching the slice with the sdxslice -M command, specify the -a jrm={on off} option to set the JRM mode. By default, it is enabled. For details, see " sdxslice - Slice operations."
Changing the mode of JRM for slices is impossible.
To disable the mode of JRM for slices, specify the -a jrm=off option to the sdxattr -S command. Changing the mode to "on" is impossible. For details, see " sdxattr - Set objects attributes."
Checking the mode of JRM for slices is impossible.
For the mode of JRM for slices, use the sdxinfo command with the -e long option and check the JRM field of the displayed slice information. For details, see " sdxinfo - Display object configuration and status information."
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 re-joining 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.
When parting the proxy with the [Operation]:[Proxy Operation]:[Part] menu in the Main Screen, set the JRM mode ("on" or "off") in the Part Proxy dialog box. The default value is "on". For details, see "Part" in "Backup(by Synchronization)."
When relating the proxy with the [Operation]:[Proxy Operation]:[Relate] menu, the mode of JRM for proxies is disabled for the related proxy volume.
When parting the proxy with the sdxproxy Part command, specify the -a pjrm={on off} option to set the mode of JRM for proxies. By default, it is enabled. For details, see " sdxproxy - Proxy object operations."
Changing the mode ("on" and "off") of JRM for proxies is impossible.
To disable the mode of JRM for proxies, specify the -a pjrm=off option to the sdxattr -V command. Changing the mode to "on" is impossible. For details, see " sdxattr - Set objects attributes."
For the mode ("on" or "off") of JRM for proxies, check the Proxy Volume Information Field in the Main Screen. For details, see "Viewing Proxy Object Configurations."
For the mode of JRM for proxies, use the sdxinfo command with the -e long option and check the PJRM field of the displayed volume information. For details, see " sdxinfo - Display object configuration and status information."
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