On Jun 26, 2007 09:53 -0700, Bryan Henderson wrote: > >md/raid already works happily with different sized drives from > >different manufacturers ... > > >So I still cannot see anything particularly new. > > As compared to md of conventional disk partitions, it brings the ability > to create and delete arrays without shutting down all use of the physical > disks (to update the partition tables). (LVM gives you that too). It > also makes managing space much easier because the component devices don't > have to be carved from contiguous space on the physical disks. > > Neither of those benefits is specific to RAID, but you could probably say > that RAID multiplies the problems they address. That's one of the reasons why I liked AIX doing RAID1 on top of LVM. It was possible to safely migrate LEs across disks by virtue of creating a RAID 1 mirror for that LE and then deleting the old copy. It wouldn't be too hard to extend the same notion to RAID 5 or RAID 6 on LVM. You could even change the RAID level and number of constituent LEs in a RAID set on an ad-hoc basis because the LVM mappings would allow this to be efficient. Unfortunately, Linux still has distinct DM and MD layers and there doesn't seem to be any work to combine the two into a more powerful single layer. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
