>> I don't completely agree here, there are ways to do snapshots without >> any >> downtime for example in a SAN environment or using filesystem or LVM >> based >> snapshot methods. However, it does not mean your snapshots are really >> consistent from the aplications point of view. > > And that's the big question: How inconsistent can things be without > shutting down > cyrus?
I think nobody can really tell you. There are several possible inconsistencies which depend on how you are doing snapshots or backups and what filesystem you are using. However, exactly the same inconsistencies will show up when your box crashes (kernel panic, power failure) and properly configured systems should survive this without loosing much. Of course, one has to make sure that the obvious is properly configured like for example disabling raid/disk write caches with no battery backup or making sure that the OS/filesystem really writes data out to the disk when the application thinks it has been written. It's not always an easy task and you will usually loose some performance by disabling those dangerous tuning things. Simon ---- Cyrus Home Page: http://asg.web.cmu.edu/cyrus Cyrus Wiki/FAQ: http://cyruswiki.andrew.cmu.edu List Archives/Info: http://asg.web.cmu.edu/cyrus/mailing-list.html