8.42. device-mapper-multipath

Updated device-mapper-multipath packages that fix several bugs and add various enhancements are now available for Red Hat Enterprise Linux 6.
The device-mapper-multipath packages provide tools for managing multipath devices using the device-mapper multipath kernel module.

Bug Fixes

When running a command on a specific device, the multipath utility did not accept device specification using the major:minor format. This bug has been fixed, and a multipath device can now be associated with the multipath command using a path device major:minor specification.
Previously, the readsector0 checker did not consider the blocksize when calculating the number of blocks to read, which led to readsector0 reading too much on 512 byte devices causing device errors. With this update, readsector0 considers the device blocksize when calculating the amount to read, and 512 byte devices now work with the readsector0 checker as intended.
Prior to this update, the code that handles multipathd sysfs devices could free a device structure while other data still pointed to it. As a consequence, the multipathd daemon could occasionally experience use-after-free memory corruption leading to unexpected termination. The sysfs device handling code for multipathd has been rewritten, and multipathd no longer frees sysfs device memory while it is still in use.
Some of multipathds prioritizers run scsi commands with long timeouts. These prioritizers do not run asynchronously and multipathd becomes busy waiting for one to timeout. Consequently, the multipathd daemon can become unresponsive for as long as 5 minutes when a path fails. With this update, the prioritizers use the "checker_timeout" option to configure their timeout. Now, prioritizer timeouts can be adjusted using the checker_timeout option to prevent multipathd hangs.
When a multipath device was reloaded outside the multipathd daemon and existing paths were removed from the device, mutipathd still treated them as belonging to a multipath device. Consequently, multipathd tried to access a non-existent path_group and terminated unexpectedly. With this update, multipathd correctly disassociates removed paths and no longer crashes when existing paths are removed by external programs.
If the multipathd daemon failed to add a path to the multipath device table, the path was incorrectly orphaned. As a consequence, the multipath utility treated the path as belonging to a multipath device, and multipathd could keep attempting to switch to a non-existent path_group. The underlying source code has been fixed, and multipathd now correctly orphans paths that cannot be added to the multipath device table.
In addition, this update adds the following


This update adds the force_sync multipath.conf option. Setting force_sync to "yes" keeps the multipathd daemon from calling the path checkers in asynchronous mode, which forces multipathd to run only one checker at a time. In addition, with this option set, multipathd no longer takes up a significant amount of CPU when a large number of paths is present.
Previously, the default path ordering often led to the Round Robin path selector picking multiple paths to the same controller, reducing the performance benefit from multiple paths. With this update, multipath reorders device paths in order to alternate between device controllers, leading to a performance improvement.
This update adds iscsi support for the "fast_io_fail_tmo" option to allow the user to modify the speed of multipath responding to failed iscsi devices.
With this update, "-w" and "-W" options have been added to multipath; the "-w" option removes the named WWID from the wwids file, the "-W" option removes all WWIDs from the wwids file except for the WWIDs of the current multipath devices.