Re: limits on raid

[David Greaves <david@dgreaves.com>]

david@lang.hm wrote:
> On Fri, 22 Jun 2007, David Greaves wrote:
> 
>> That's not a bad thing - until you look at the complexity it brings - 
>> and then consider the impact and exceptions when you do, eg hardware 
>> acceleration? md information fed up to the fs layer for xfs? simple 
>> long term maintenance?
>>
>> Often these problems are well worth the benefits of the feature.
>>
>> I _wonder_ if this is one where the right thing is to "just say no" :)
> so for several reasons I don't see this as something that's deserving of 
> an atomatic 'no'
> 
> David Lang

Err, re-read it, I hope you'll see that I agree with you - I actually just meant 
the --assume-clean workaround stuff :)

If you end up 'fiddling' in md because someone specified --assume-clean on a 
raid5 [in this case just to save a few minutes *testing time* on system with a 
heavily choked bus!] then that adds *even more* complexity and exception cases 
into all the stuff you described.

I'm very much for the fs layer reading the lower block structure so I don't have 
to fiddle with arcane tuning parameters - yes, *please* help make xfs self-tuning!

Keeping life as straightforward as possible low down makes the upwards interface 
more manageable and that goal more realistic...

David