Re: RAID5 reconstruction ?

[John Robinson <john.robinson@anonymous.org.uk>]

On 30/05/2009 17:16, Maxime Boissonneault wrote:
> John Robinson a écrit :
>> On 30/05/2009 15:06, Maxime Boissonneault wrote:
>>> I don't know how it goes for Linux, but hasn't ZFS been developped 
>>> exactly for that purpose ? From what I understand, ZFS manage both 
>>> the file system and the RAID features at once. Therefore, the "raid" 
>>> part knows where are the files and the filesystem knows about the 
>>> raid. Reconstruction is then done intelligently (not reconstructing 
>>> unused space).
>>
>> Yes, ZFS can do this, but ext4 and md could do it too, and probably 
>> will at some point. I prefer separating the layers, then I can switch 
>> one and not the other, e.g. start using a hardware RAID controller 
>> instead of md.
>>
> Chances are that the hardware controler would not be compatible with 
> mdadm and you would have to backup and copy your data anyway.

Sure, but I can keep my filesystem, which I've chosen for whatever 
filesystem features it has, rather than having chosen it because it does 
RAID itself.

It would be nice if RAID controllers and md used the same metadata, 
though, wouldn't it, so we could swap discs between controllers and 
everything would Just Work? Umm, do any RAID controllers support SNIA 
DDF? I think md does (or soon will)...

Cheers,

John.
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