On Sun, August 16, 2009 4:54 am, Jon Hardcastle wrote: > Hi quick Q.. I have a 6 drive array made up of 4 500GB's and 2 750GB's. > > I know the array will only take on a size based on the smallest drive. To > that end as I phase drives out based on usage etc I replace them with the > best value drive I can lay my hands on (upto 1TB~ as i have read a raid 5 > array of drives over that size approx start to cause problems with read > failures on re-builds - but that is for another thread) > > So my array is currently ~2.5GB with 2x250GB currently not in use and I am > about to phase out a 500GB and replace with a 1TB. Now i have read that > you are better of creating a auto detect raid partition on the drive and > adding that rather than adding the entire drive (so sda1 not sda). This is > where my question comes in. I have read that 2 1TB(or whatever size) can > be different block sizes and hence adding a partition that is the entire > drive can cause problems as these sizes will differ. This was a topic of a recent thread on this list. Apparently there is an industry standard which sets out exactly how many sectors a 1TB or 2TB drive should be, and it seems that all drive manufactures adhere to this. > > Can anyone tell me what truth there is in this? Should I actually create a > partition that is always going to be a nice multiple size smaller so i > can smooth over the bumps? Personally I never create a single partition for an md array. I either use the whole drive, or create a number of partitions for different arrays. I also avoid in-kernel autodetect. The question of what "best" may well come down to the start up scripts that your distro uses and any hidden assumptions that might be in them... I guess that isn't very helpful though... I can say that either approach can be made to work fine. The one issue that you particularly need to be careful off is the boot sector. Partitions always leave room for a boot sector. If you don't use partitions and you want a separate boot sector, then v1.2 metadata is the thing to choose.... > > (also anyone know if raid5 to raid 6 native support is anywhere near?) Yes. It works with 2.6.30 (or preferrable 2.6.31) and the devel-3.1 branch from my git tree git://neil.brown.name/mdadm NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
