Re: Question about raid robustness when disk fails

[Asdo <asdo@shiftmail.org>]

Goswin von Brederlow wrote:
> Michael Evans <mjevans1983@gmail.com> writes:
>   
>> Why doesn't the kernel issue a pessimistic alternate 'read' path (on
>> the other drives needed to obtain the data) if the ideal method is
>> late.  It would be more useful for time-sensitive/worst case buffering
>> to be able to customize when to 'give up' dynamically.
>>     
>
> That is a verry good question. I look forward to seeing patches for this
> from you. :) I think it isn't done because nobody has bothered to write
> the code yet but maybe I'm wrong and it would make the code too
> complicated.
>   

This is probably more complicated than allowing a timeout to be set at 
the MD layer or block-device layer, isn't it?

Which would be just as good I think.

Is it possible to cancel a SATA/SCSI command that is being executed by 
the drive?
(it's probably feasible only with NCQ disabled anyway, but it's easy to 
disable NCQ)


It's a pity we have to rely on TLER, this narrows the choice of drives a 
lot...