TLER for RAID10?

P

Psychor

Limp Gawd
Joined
Dec 22, 2007
Messages
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I've read that TLER (as WD calls it) is desired in a drive when running, for example, a RAID 5 array. However, if I plan to run a RAID10 array with 2TB drives do I still need to use drives that support TLER or the equivalent? I've run a RAID0 with WD Raptors and a RAID1 with WD Greens for ages without an issue but I'd like a more definitive answer if possible. ;)

Thank you.
 
TLER will not effect basic RAID levels of 1 and 0. Since 10 is comprised of both of those TLER is not something to worry about.
 
TLER stops a single drive from continuously trying to read a bad sector on one of its platters - since this can take up to 30 seconds, it can fool the RAID controller into thinking that the drive is dead. At this point the controller will drop the drive from the array.

TLER limits this behaviour to 7 seconds, so that the drive will inform the controller that much quicker that it couldn't read or write the data. It is then up to the controller to handle that situation. TLER is about drive response times under error conditions, not parity calculations.

TLER and RAID topology are unrelated, yet one can affect the other. TLER is recommended under redundant topologies such as RAID 5 & 6, and also RAID levels 1, 10 and 0+1 because the missing data can be recovered from another drive, so rather than risk dropping the drive, cut short its error recovery cycle and get the data from a redundant copy (or calculate it from parity).

TLER is NOT recommended for RAID 0, because there is no redundant copy of data anywhere, so therefore you need the drive to try as hard as possible to recover the data.

A good rule of thumb is that hardware-based and firmware-based RAID controllers require TLER. For more information on TLER, look here.
 
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