I've been asked about using operating system snapshots to make backups of live repositories. These could be filesytem snapshots like ZFS or FreeBSD's UFS2, or block level snapshots like Linux's LVM, or maybe even a Windows shadow copy. The reasons for using snapshots, rather than "svnadmin hotcopy", are that it's a better fit with the overall backup strategy or that it is faster or requires less disk space or less IO. This has also been discussed on the mailing lists, e.g. http://svn.haxx.se/users/archive-2012-02/0233.shtml As far as I know the snapshot method should work provided there are no bugs in Subversion or the snapshot code but it would be good to have more confidence that it works.
One of our customers asked about locking the FSFS write-lock file before taking the snapshot as this would halt writes and make the repository quiescent. It's certainly possible to do it, I wrote a program that calls the private API svn_fs_fs__with_write_lock, but calling a private API is a hack and I need to lock the rep-cache as well. So I was wondering whether we should introduce a public API to do this properly either at the svn_fs_ or svn_repos_ level. For FSFS this would stop writes while allowing reads. A BDB implementation would probably stop reads as well. -- Certified & Supported Apache Subversion Downloads: http://www.wandisco.com/subversion/download
