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.
