4.12. cmirror

Previously, when successively activating and deactivating cluster mirrors, cmirror could fail to initialize the mirrors properly. Consequently, any I/O operations to the device and further LVM commands became unresponsive. With this update, cmirror has been modified to fix this bug; however, the problem can still occur after a large number of iterations.

The cluster mirror daemon sends information between cluster nodes to keep the mirror log state consistent. Information about the state and health of the mirror and its devices is gathered as needed from the daemon. Some of the information does not change after the device has reached a certain state, for example when the mirror becomes "in-sync", while other information can change, for example the health of the log device in response to a failure. To limit the amount of such requests and reduce the load on the network, processing of information which cannot change is done locally. Previously, also requests for information regarding the health of the log device - which ultimately controls the fault handling behavior of the mirror - were processed locally, which caused the daemon to miss the failure of the log device on a remote machine. With this update, the information is requested from the cluster so that log device failures are detected and processed as expected.

Prior to this update, requests for information about the health of the log device were processed locally. As a consequence, the cluster mirror daemon could not detect log device failures on remote machines. With this update, the information is requested from the cluster so that log device failures are detected and processed as expected.

Prior to this update, the cmirror utility could fail to initialize the mirrors correctly when successively activating and deactivating cluster mirrors. As a consequence, any I/O operation to the device and further LVM commands became unresponsive.This update modifies the underlying code so that the problem only occurs after a large number of iterations.