Re: mdadm and TLER (Time Limited Error Recovery)

[Maurice Hilarius <maurice@harddata.com>]

Iustin Pop wrote:
> ..
>> Anyways, clarification...
>> The only reason for TLER (Time Limited Error Recovery) is to behave
>> "friendly" toward RAID controllers that timeout disks.
>> In fact, md does not timeout disks as many Hardware RAID controllers do.
>> So, from md's point of view, TLER is useless, i.e. it has no benefit.
>>     
>
> I'm sorry but I disagree here. *Especially* because md is used over
> normal SATA controllers most of the time, TLER is beneficial because the
> drive doesn't go catatonic for minutes at a time trying to recover a bad
> sector, which would (because md doesn't timeout disks) cause md to hung
> up the whole device. TLER will allow md to see the error quickly and
> attempt to rewrite (read) or retry/fail the disk (write) for a bad the
> sector.
>
> Just my understanding of the md stack.
>
> regards,
> iustin
>
>   
I agree.
Before WD implemented this we would see cases quite often where a 
perfectly good drive would get "kicked out"
of a RAID as frequently or even more often, than on a hardware RAID.
TLER management seems to have eliminated most of these cases.



-- 
Regards, Maurice