We want to store our backups of our svn repositories as a flat file. We'd like to tar/zip the whole hotcopied directory. I know that we could dump it to a flat file but let's pretend that we'd rather use hotcopy instead. Are there any gotchas (i.e. byte-order caveats) with zipping/tarring svn repositories?
SVN repositories are simply files in a directory structure. So the short answer is yes, it is safe !
to be on the safe side you can always run
svnadmin dump /some/repo | bzip2 > /some/file
more here. this is the backup / migration method for svn.
on the other hand... i've been zipping repositories few times [ although they were idle ] and never had any problems with recovering, but recoveries were done on the same architecture.