Re: Postgresql data integrity during RAID10 drive rebuild

On Wed, 2006-11-29 at 14:16, Vivek Khera wrote:
> On Nov 29, 2006, at 2:39 PM, Scott Marlowe wrote:
>
> >> Sounds good. According to LSI, the drive will take 8 hrs to rebuild a
> >> 146GB disc (at a 30% rebuild rate), so doing this in the middle of
> >> the
> >> day is not ideal.
> >
> > The rebuild time also tends to depend on how full the array is. If
> > you're only using 5% or so, it won't take the full 8 hours they're
> > projecting.
>
> But how does the RAID card know what is and what is not "full" in the
> unix file system stored on it? It has to rebuild the entire drive.

Not sure how they do it exactly, but it seems a lot of RAID controllers
know which parts of a drive have been written to and which haven't. I
recall seeing it happen on rebuilding a RAID 5 on an old LSI card.

It could just be that it's a lot faster if it's got zeros on a block and
can short circuit the parity there.

As for RAID 1+0, not sure if it will be faster or not.