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As noted in Talk:Error recovery control#Completely agree - preoccupation with hardware vs. software RAID, this should improve the things (the while article could use much more work, of course) |
→Standalone vs. RAID considerations: Meh, my bad, fixed |
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It is best for TLER to be "enabled" when in a RAID array to prevent the recovery time from a disk read or write error from exceeding the RAID implementation's timeout threshold. If a drive times out, the hard disk will need to be manually re-added to the array, requiring a re-build and re-synchronization of the hard disk. Enabling TLER seeks to prevent this by interrupting error correction before timeout, to report failures only for data segments. The result is increased reliability in a RAID array.
In a stand-alone configuration TLER should be disabled. As the drive is not redundant, reporting segments as failed will only increase manual intervention. Without a hardware RAID controller or a software RAID
In a software RAID configuration whether or not TLER is helpful is dependent on the operating system. For example in FreeBSD the ATA/CAM stack controls the timeouts, and is set to progressively increase the timeouts as they occur. Thus, if a desktop disk without TLER starts delaying a response to a sector read, FreeBSD will retry the read with successively longer timeouts to prevent prematurely dropping the disk out of the array.
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