Mean Time to Repair (MTTR)

Mean Time To Repair (MTTR) is the amount of time it will be expected to take to get
a device fixed and back into production.

 

MTTR的计算：

 

For a hard drive in a redundant array, the MTTR
is the amount of time between the actual failure and the time when, after noticing the
failure, someone has replaced the failed drive and the redundant array has completed
rewriting the information on the new drive. This is likely to be measured in hours. For a
nonredundant hard drive in a desktop PC, the MTTR is the amount of time between
when the user emits a loud curse and calls the help desk, and the time when the replaced
hard drive has been reloaded with the operating system, software, and any backed-up
data belonging to the user. This is likely to be measured in days. For an unplanned reboot,
the MTTR is the amount of time between the failure of the system and the point in
time when it has rebooted its operating system, checked the state of its disks (hopefully
finding nothing that its file systems cannot handle), restarted its applications, its applications
have checked the consistency of their data (hopefully finding nothing that their
journals cannot handle), and once again begun processing transactions. For well-built
hardware running high-quality well-managed operating systems and software, this may
be only minutes. For commodity equipment without high-performance journaling file
systems and databases, this may be hours, or, worse, days if automated recovery/rollback
does not work and a restore of data from tape is required.

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