Disk Device dm-5 is busy
 

guyz,

what is dm-5 means, we got this alert for one of our critical server.Here is the alert

Target Name=drug1.system
Target type=Host
Host=drug1.system
Occurred At=Apr 1, 2012 6:22:38 PM EDT
Message=Disk Device dm-5 is 99.73% busy.
Metric=Disk Device Busy (%)
Metric value=99.73
Disk Device=dm-5
Severity=Critical
Acknowledged=No

can you please explain me

dm-5 is a a multipath device.

If you run "multipath -l -v2" it will show you your multipath configuration.

Within that output you can search for dm-5 - you should see something similar to:
mpathf (360060e8006d142000000d14200005e03) dm-5 HITACHI,OPEN-V
size=1.0T features='1 queue_if_no_path' hwhandler='0' wp=rw
`-+- policy='round-robin 0' prio=-1 status=active
|- 2:0:0:3 sdf 8:80 active undef running
`- 3:0:0:3 sdj 8:144 active undef running

Note that yours likely wouldn't show Hitachi Open-V unless you happened to be using a Hitachi USP/VSP disk array so above is only example.
In the example it shows that dm-5 is multipath device mpathf and that it is comprised of disks /dev/sdf and /dev/sdj.

The message you got is from some sort of monitoring software you're running. Without knowing what it is we can't really comment on the software. However the busy % suggests the multipath disk (and hence the underlying /dev/sd* disks) is very heavily used so your software is letting you know so you can address it if possible. How you would address it would depend on many variables such as how you had the disk configured (e.g. are you using partitions? meta disks? LVM?) and what it is running (e.g. Database data files? User home directories? something else?). An obvious tactic for trying to address it would be to try to move some of what is using it off to another disk (or multipath device) but that isn't always possible. Again you'd have to know what is using it.