Linux LVM Mirroring Sucks
I'm using the ability of Linux's Logical Volume Manager (LVM) to mirror data on to two drives. It's horrible. It requires either a third disk (which can't be the same disk as either of the two components of the mirror, but can be a software RAID (Linux MD) of both disks), or to resynchronize at every boot (using "corelog").
Additionally, it has been reported that if a physical volume (PV) is missing, any volume group (VG) using that PV is "read-only" and any logical volumes (LVs) are also "read-only". This means that you cannot use the mirror in degraded mode (it can be mounted "read-only", which is not too useful). Further, the use of the component of the mirror is predicated on using the component name (and not the mirror name), which is inconvenient.
Additionally, there is very little documentation about LVM's mirroring capabilities (probably because they are so weak).
So, while LVM mirroring can be used and it will protect your data, it is not a replacement for Linux Software RAID (MD), and it sucks.