I'm about to set up a new nas and basically want to know if it's a bad or a good idea to have one lvm volume on multiple mirrored mdadm arrays, kind of like raid 10. I thought this would make it easier to expand the volume by just adding a new raid1 array to the volume. Is this smart or should I just go with plain mdadm?
The up side to using lvm this way is that it does make expanding easy and the new drives don't have to be the same size. On the other hand, a 4 disk mdadm raid10 configured to use the offset striping mode can give seqential read performance near that of a 4 disk raid0, but an lvm stripe on top of two mdadm raid1s only has the performance of two disks.