MDMPD(8)MDMPD(8)NAMEmdmpd - daemon to monitor MD multipath devices
SYNOPSISmdmpdDESCRIPTION
Enterprise storage requirements often include the desire to have more
than one way to talk to a single disk drive so that in the event of
some failure to talk to a disk drive via one controller, the system can
automatically switch to another controller and keep going. This is
called multipath disk access. The linux kernel implements multipath
disk access via the software RAID stack known as the md (Multiple
Devices) driver. The kernel portion of the md multipath driver only
handles routing I/O requests to the proper device and handling failures
on the active path. It does not try and find out if a path that has
previously failed might be working again. That's what this daemon
does. Upon startup, the daemon will fork and place itself in the back‐
ground. Then it reads the current state of the md raid arrays, saves
that state, and then waits for the kernel to tell it something inter‐
esting has happened. It then wakes up, checks to see if any paths on a
multipath device have failed, and if they have then it starts to poll
the failed path once every 15 seconds until it starts working again.
Once it starts working again, the daemon will then add the path back
into the multipath md device it was originally part of as a new spare
path.
OPTIONS
None. This is a very simple program that only does one thing.
FILES
/proc/mdstat
If you're using the /proc filesystem, /proc/mdstat lists all active md
devices with information about them. mdmpd requires this to find
arrays to monitor paths on and to get notification of interesting
events.
v0.3MDMPD(8)
