> if something rsync-ish looks like the right kind of > thing this might be of interest... > > http://www.dirvish.org/ > > dirvish is a backup utility that does snapshot style > backups using rsync. the documentation page also > has links to some useful-looking rsync documentation > and links to sites for other, similar projects.
The problem with any type of an rsync utility is in its asynchronous nature. In computer science, the main premise of a distributed FS are synchronous, real-time updates to all storage nodes on which the FS lays. Consider the following scenario: you have two campuses of developers that are accessing the storage system. Obviously if the central system is a single NFS node, it is a single point of failure. So adding another system gives you N+1, and leaves you with two storage nodes on each campus. The developers write to the storage node that is local to them, and the data gets replicated to the remote node in real time, which keeps both groups of users current on content. However, if the data between systems is replicated in an asynchronous manner (for example, once per day), statistically speaking, there is a very high chance that a single file will be modified by two people on different campuses at the same time, or entire directories removed, added etc. In practice, this holds especially true for campuses which are in different time zones (for example EU vs. US). With rsync, these things do not occur in real time, so two developers could be stepping on each other's toes without knowing it, possibly hours after the fact! To solve the problem, you need a distributed FileSystem capable of locking semantics and failover. If you are just trying to solve the availability part of the problem, you need automatic and transparent failover. rsync and friends do not offer either of these capabilities, just a detection of a conflict, which is not the solution to the problem. It's like asking for pistachio ice cream cone and getting a chocolate bar instead. This message posted from opensolaris.org _______________________________________________ opensolaris-discuss mailing list opensolaris-discuss@opensolaris.org
