Using fast disk takeover
PowerHA® SystemMirror® automatically detects failed volume groups and initiates a fast disk takeover for enhanced concurrent mode volume groups that are included as resources in nonconcurrent resource groups.
Fast disk takeover is especially useful for fallover of enhanced concurrent mode volume groups made up of a large number of disks. This disk takeover mechanism is faster than disk takeover used for standard volume groups included in nonconcurrent resource groups. During fast disk takeover, PowerHA SystemMirror skips the extra processing needed to break the disk reserves, or update and synchronize the logical volume manager (LVM) information by running lazy update.
Fast disk takeover has been observed to take no more than 10 seconds for a volume group with two disks. This time is expected to increase very slowly for larger numbers of disks and volume groups. The actual time observed in any configuration depends on factors outside of PowerHA SystemMirror control, such as the processing power of the nodes and the amount of unrelated activity at the time of the fallover. The actual time observed for completion of fallover processing depends on additional factors, such as whether or not a file system check is required, and the amount of time needed to restart the application.