On 09/03/14 11:43 AM, Stephen Harris wrote: > On Sun, Mar 09, 2014 at 11:28:07AM -0400, Digimer wrote: >> Would you mind elaborating on this? If a snapshot is a point-in-time >> image of a VM (or even normal FS), why would DB backups be at risk >> (assuming things like fsync are used)? >> >> I'm asking in general terms... no idea if this is something AWS specific. > > Database disk snapshots may include "transactions in flight" and the > on-disk image may not be in a consistent state. Databases such as Oracle > try to work around this by ensuring that writes occur in a specific order > and have a good "recovery" process (each data file has a change number; > determine the best change number to start from, roll forward from there > to recover, then roll back any incomplete transactions) but it's considered > "crash recovery" and shouldn't be part of BAU activity. Other databases > may not be so good at recovery (mysql?) and so you run the risk of database > corruption if you need to restore the snapshot. > > If you rely on disk snapshots then it's recommended you do a proper db dump > before the snapshot is taken, so that you can recover the database from > the dump file and not the snapshot. Thanks for the reply, Stephen. I also replied to Nico, and my comments there can be directed to you, as well. :) -- Digimer Papers and Projects: https://alteeve.ca/w/ What if the cure for cancer is trapped in the mind of a person without access to education?