Managing RAID on Linux

RAID and syslog

The md driver uses the system logging daemon (syslogd) to report pertinent information and errors relating to the kernel RAID subsystem. md reports information using the kern facility (LOG_KERN). Table 7-1 outlines the priorities at which the RAID subsystem reports information to the kernel ring buffer.

Table 7-1. Software RAID log reporting

facility.priority	Information reported
kern.info	Status changes, including insertion and removal of member disks, resynchronization progress, and startup and shutdown notices. In general, any information about an array that does not affect performance or continuing operation.
kern.err	Error messages about problems that either prevent an array from being started, created, or modified, or affect array operation in a nonfatal manner. This includes disk failures and consequent insertion of spare disks, initialization and completion of reconstruction, and problems with the configuration file.
kern.alert	Catastrophic errors that prevent a running array from continuing to operate. Problems logged at this level usually result in the crash of a running array or the inability to start an array that is not running. These issues include memory problems, low-level device problems, and fatal errors that occur during the reconstruction process.

Many distributions log this information to some combination of /var/log/messages and /var/log/warn. The following line in /etc/syslog.conf captures all kernel-level messages:

kern.*          /var/log/kernel

After adding ...