the Linux software raid stack supports data scrubbing (reading disks in the raid array and looking for bad sectors, and when bad sectors are found using information from other disks or from parity to rewrite the bad sectors with good data). However, the mdadm package did not make use of this functionality. This package adds a cron job to /etc/cron.weekly to check disks for bad sectors and repair them when found. (BZ#233972)

the mdadm man page contained several typos and was not clear on the proper usage of a number of mdadm options. The typos have been removed and notes and clarifications have been added so that the man page now better reflects the proper usage and limitations of the mdadm command. (BZ#434670 , BZ#434671 , BZ#489476)

mdadm did not recognize the "-N" and "-Y" short options, although it recognized their long equivalents ("--name" and "--export") and they were listed as valid in mdadm --help. Mdadm now recognizes these short options. (BZ#478977)

a new raid-check script (see the enhancement note below) attempted to check arrays that were not checkable. The script first retrieved a list of active arrays from /proc/mdstat then attempted to write "check" to the sync_action element of each array's sysfs entry. Non-redundant arrays (such as linear and raid0 arrays) do not have a sync_action entry in sysfs, however. Note: this did not prevent the script from checking arrays that could be checked but did cause cron job output errors to be e-mailed to the system administrator. The raid-check script now checks for a sync_action element in sysfs before writing to it. (BZ#513473)

with this update mdadm has new functionality to enable "data scrubbing" on redundant arrays. Data scrubbing looks for bad sectors on drives in redundant arrays and fixes the bad sectors using data from other drives to reconstruct sectors that return read errors. Note: data scrubbing is on by default in this new package. It runs once per week and may cause some performance degradation while it is running. If users wish to disable this feature for performance reasons, or if they wish to control what type of check is performed on arrays, or which arrays to check at all, edit the file /etc/sysconfig/raid-check. Details of how to set options are included in the file as comments. (BZ#513200)