On 17 Jun 2010, at 16:29, Andrew Deason wrote: > If you're only using volumes for home directories, or things like group > collaboration space, then RO volumes are not very useful to you.
Actually, that's definitely not true in my experience. See below. > As you mentioned, they can also 'kinda' be used for backup purposes, [ snip ] > I definitely wouldn't recommend that for home dirs or anything like that, > though, since from the user's perspective it looks like their data just > suddenly went back in time by a day. Usually it's not much better than > just having real backups. I'd strongly recommend considering them for this use - alongside a real backup solution. As a site which lost a third of it's homedirectories in a fire, we've got real world experience of how painful the restoration process can be. As a result, we make nightly disk->disk backups of all of our AFS data using the read-only volume mechanism. Should our primary computing site disappear in a ball of flame or (perhaps more likely) a RAID controller decided to spew garbage across a disk array, we can restore user data within a matter of minutes. I'm probably preaching to the converted here - but backups are completely unimportant. It's restores that are vital. When designing your backup solution, you have to consider how you get that data back, and what you get that data back onto. If your computing centre is hit in a meteor strike - do you have the disk capacity to restore your critical data? If you don't have it, how quickly can you obtain it? Do you have to wait for an insurance claim to be processed before you can do so? And so on ... Once you've got the disk capacity - what's the fastest that you can spool data out of your current backup system onto those disks? At that rate, how long will it take to do the restore? We ran those figures a while back, and decided that it made much more sense to maintain disk-based backups in parallel with our production AFS data. This means that should the proverbial meteor strike, we are just one quick operation away from restoring all of our data (albeit, on a downgraded service). We also keep tape backups, both for archival purposes, and for additional security. But our rapid response plan is to promote the read-only. Cheers, Simon. _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
