Grow LVM RAID10? RHEL LVM has supported RAID4/5/6 as of 6.3 and RAID10 as of 6.4. It's well-known that mdadm won't let you `--grow` raid10, my question is whether this is a limitation of LVM RAID10 too? If it is possible, what are the downsides of LVM RAID10 versus LVM on top of md RAID10?

According to the Gentoo Wiki, it is possible in certain circumstances, but probably not desirable:

> It is not possible to RAID10 an existing volume, **nor reshape the RAID10 across more/less PVs** , nor to convert to a different RAID level/linear volume, **It is possible to extend a RAID10 across additional PVs, but they must be added in multiples of the original RAID10** (which will effectively linearly append a new RAID10), **or --alloc anywhere must be specified (which can hurt performance)**. In the above example, 4 additional PVs would be required without --alloc anywhere.

In addition LVM RAID10 is more restricted than the md RAID10 (eg it requires an even number of drives):

> LVM syntax requires the number of PV be multiple of the numbers stripes and mirror, even though RAID10 format does not