I started using it about a month ago after being a long time ZFS user. I have 15 disks spread between 7 servers for a total of 101TB of raw disk space. With 5 of the servers being single board computers holding 1-2 hard drives each. Each drive is formatted with XFS. Moosefs will take care of all data sync and the keep up wit the number of copies. For normal media files I have it set to two copies so moosefs will make sure there are 2 copies on different servers. and for more important data I have it set to 3 copies. This is can be set per folder level or inherited from the mount. It has no problems handling drives of different sizes. With my current hardware of all HDD and no SSD I have no problems hitting 2+gbits of reads and writes which is more than enough for my needs.
It also has a nice webUI
It also has a nice webUI