Data Domain - suddenly monitoring shows disk unknown

Sometimes when you monitor data domain your monitoring software can suddenly report disk as "UNKNOWN" however data domain works as normal.
This is caused by data domain management services misbehavior.
To resolve it you should run below commands:

1. SSH to your data domain

2. Enter SE mode:

system show serialno
(make note of the serial number)
priv set se
(use the serial number as the password)

3. Run the following:

reg set config.crontab.diskinfo_reset = "*/5 * * * * root /bin/killall -9 ssm"

4. Wait for at least 10 minutes and after that time run this:

reg removekey config.crontab.diskinfo_reset