Note: Making a raw file-level backup of a SVN repository is not advisable. There may be open files, files that changed while the backup is running, etc. So you will need to use one of the hotcopy / dump methods to get a good "snapshot" of the repository state for inclusion onto a backup tape/disk/set.
If you want to backup everything, including server-side hook scripts and the like which are stored under the repository directory, take a look at "svnadmin hotcopy". It's essentially an rsync (but not quite) of the origin repository directory. The hotcopy directories (since they only change once per day, or whenever you do the hotcopy) are ideal for being used to backup the repository.
The "svnadmin dump" is more suitable for long-term archival of the SVN repository because it stores the data in platform-neutral format. It will be much larger then the original repository was (even with gzip -5) and will take a long time to perform the dump.
The third option is to run a hot-spare system using the svn sync. Except that this does not give you generational backups, so you still need to use either hotcopy/dump as well.
Personally: I prefer hotcopy for daily backups, then using rdiff-backup to make a backup of the hotcopy directory or our main backup server. The rdiff-backup step gives me the ability to go back to any day within the past 26 weeks (configurable). Combined with the use of generational media, I have multiple copies of the rdiff-backup target directory.
(rsnapshot would also be a good choice.)
I'll also make svnadmin dumps every few months, but it takes a long time to do, uses up a lot of disk space (3x for us) and has few advantages compared to the rdiff-backup of the hotcopy directory.