--- On Sun, 16/8/09, NeilBrown <neilb@xxxxxxx> wrote: > From: NeilBrown <neilb@xxxxxxx> > Subject: Re: Software, Raid 5, Different Size Drives. > To: Jon@xxxxxxxxxxxxxxx > Cc: linux-raid@xxxxxxxxxxxxxxx > Date: Sunday, 16 August, 2009, 11:45 PM > 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 > Any idea where i find out this 'industry standard'? My setup is build on drives that have a partition on them, so the finer points over the pro's and con's of this are moot for me.. until i come to replace the array. Perhaps someone can tell me tho. If I do use a partition on the 1TB drive, and it is is x blocks big. If i add another 1TB drive that is x +/- 10 blocks in size. Will the array just use the size of the smaller and grow accordingly? ----------------------- N: Jon Hardcastle E: Jon@xxxxxxxxxxxxxxx 'Do not worry about tomorrow, for tomorrow will bring worries of its own.' ----------------------- Send instant messages to your online friends http://uk.messenger.yahoo.com -- 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
