[Dovecot] RAID1+md concat+XFS as mailstorage

[Костырев Александр Алексеевич]

>- RAID1 pairs, plus some kind of intelligent overlay filesystem, eg 
>md-linear+XFS / BTRFS. With the filesystem aware of the underlying 
>arrangement it can theoretically optimise file placement and 
>dramatically increase write speeds for small files in the same manner 
>that RAID-0 theoretically achieves. (However, still no protection 
>against "silent" single drive corruption unless btrfs perhaps adds this 
>in the future?)

not only "silent" single drive corruption problem but as I stated in start of topic - crash of first pair.