Disk Survey

Surveying the disks of the world


Wikipedia: http://en.wikipedia.org/wiki/Time-Limited_Error_Recovery

These three acronyms stand for:

  • TLER — Time Limited Error Recovery
  • ERC — Error Recovery Control
  • CCTL — Command Completion Time Limit

All of these mean one thing, they are a way to tell a SATA drive to limit the time it does error recovery since it may cause the drive to be dropped from the RAID. The disk drive than stops short of its fully recovery attempt and in doing so chooses to increase the rate of unrecoverable media errors, most times this time is limited to about 10 seconds where the maximum time for error recovery is around 30 seconds or even unlimited.

For SAS drives there is a standard mode parameter to set the maximum time for error recovery though not all drives implement it.

Not all drives implement these mechanisms, in fact, the drive manufacturers now tend to remove this feature from the regular consumer drives in order to push users to buy the higher grade drives such as the Black and Red drives that are intended for the Enterprise and NAS workloads.