Justin Piszcz <[EMAIL PROTECTED]> writes:
> On Fri, 19 Oct 2007, Alberto Alonso wrote:
>
>> On Thu, 2007-10-18 at 17:26 +0200, Goswin von Brederlow wrote:
>>> Mike Accetta <[EMAIL PROTECTED]> writes:
>>
>>> What I would like to see is a timeout driven fallback mechanism. If
>>> one mirror does not return the requested data within a certain time
>>> (say 1 second) then the request should be duplicated on the other
>>> mirror. If the first mirror later unchokes then it remains in the
>>> raid, if it fails it gets removed. But (at least reads) should not
>>> have to wait for that process.
>>>
>>> Even better would be if some write delay could also be used. The still
>>> working mirror would get an increase in its serial (so on reboot you
>>> know one disk is newer). If the choking mirror unchokes then it can
>>> write back all the delayed data and also increase its serial to
>>> match. Otherwise it gets really failed. But you might have to use
>>> bitmaps for this or the cache size would limit its usefullnes.
>>>
>>> MfG
>>> Goswin
>>
>> I think a timeout on both: reads and writes is a must. Basically I
>> believe that all problems that I've encountered issues using software
>> raid would have been resolved by using a timeout within the md code.
>>
>> This will keep a server from crashing/hanging when the underlying
>> driver doesn't properly handle hard drive problems. MD can be
>> smarter than the "dumb" drivers.
>>
>> Just my thoughts though, as I've never got an answer as to whether or
>> not md can implement its own timeouts.
>>
>> Alberto
>>
>>
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>
> I have a question with re-mapping sectors, can software raid be as
> efficient or good at remapping bad sectors as an external raid
> controller for, e.g., raid 10 or raid5?
>
> Justin.
Software raid makes no remapping of bad sectors at all. It assumes the
disks will do sufficient remapping.
MfG
Goswin
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