When an error is found on a desktop edition hard drive, the drive will enter
into a deep recovery cycle to attempt to repair the error, recover the data
from the problematic area, and then reallocate a dedicated area to replace
the problematic area. This process can take up to 2 minutes depending on the
severity of the issue. Most RAID controllers allow a very short amount of
time for a hard drive to recover from an error. If a hard drive takes too
long to complete this process, the drive will be dropped from the RAID array.
Most RAID controllers allow from 7 to 15 seconds for error recovery before
dropping a hard drive from an array. Western Digital does not recommend
installing desktop edition hard drives in an enterprise environment (on a
RAID controller).
Western Digital RAID edition hard drives have a feature called TLER (Time
Limited Error Recovery) which stops the hard drive from entering into a deep
recovery cycle. The hard drive will only spend 7 seconds to attempt to
recover. This means that the hard drive will not be dropped from a RAID
array. While TLER is designed for RAID environments, a drive with TLER
enabled will work with no performance decrease when used in non-RAID
environments.
