My question is more for the mdraid at the bottom of the stack than anything. I'm also a little curious about performance of something webdav vs. samba vs. sshfs (sshfs usually wins out and webdav does not strike me as particularly efficient)
Wouldn't the blocks all be cached locally for the most part? WebDAV is being used as a write behind log/backup. It should be as fast as local access through a file system created over mdraid loopback block devices ...
you're right (see the sibling comment chain), I didn't realize this was just being done on local disk with periodic backup, thought webdav was below it all!