Say I have a bunch of servers that access a gluster mount to serve files via http. Files are sourced internally, and are copied from an internal server to the gluster mount on one of the download servers, and in that way changes are propagated throughout - Should I have files copied directly to the servers that host the gluster mount, or should I continue to copy them to the servers that access the gluster mount?
Do not modify the underlying bricks that create GlusterFS volumes, as you'll create inconsistencies that will require triggered correction or even manual intervention.
If your servers are providing content via HTTP and are backed by GlusterFS, use the FUSE mount on a Gluster client to read / write data. This is similar to the concept that you shouldn't modify underlying block devices that constitute a RAID.