On Wednesday May 13, sandeepksinha@xxxxxxxxx wrote: > Hi, > > On Wed, May 13, 2009 at 10:01 AM, Neil Brown <neilb@xxxxxxx> wrote: > > On Tuesday May 12, lrhorer@xxxxxxxxxxx wrote: > >> > >> But doesn't creating the array with the drive wipe the contents? If so, it > >> doesn't seem to me this provides much redundancy. > > > > No. Creating an array does not wipe the contents. > > It might cause a resync which will copy contents from one drive to the > > other and I don't promise which one. > > However if you: > > > Now, my question is that what if I create a RAID1 with 100 disks on each side. > Do you mean to say that there will be unnecessary resync happening > there as well, that too for unallocated/written data. I'm not sure what "100 disks on each side" means. Do you mean a raid1 across 100 devices? i.e. 100 copies of each block? In any case, md has no concept of unallocated/written data. Every block is potentially meaningful and needs to be copied for resync. I have had thoughts about keeping track of which blocks have been used so that 'TRIM' can be passed down. But it is a long way from being a reality. > > If thats the case, we surely need to handle these two situations > differently (1) which neil mentioned (2) the one I mentioned above. > > Remember I referring to the case of creation. > > > mdadm -C /dev/md0 --level 1 -n 2 /dev/foo missing > > mdadm /dev/md0 --add /dev/bar > > > > then the contents on /dev/foo will not be changed (except for a few K > > at the end for the metadata) and then all of foo will be copied to > > bar. > > > > Will the create happen at the first place? I don't understand this question, sorry. 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
