Comments for Easy software upgrades, AppLogic-style at http://www.enkiconsulting.net , comment 0 to 2 out of 2 comments http://www.enkiconsulting.net Fri, 21 Nov 2008 08:17:58 +0100 FeedCreator 1.7.2 http://www.enkiconsulting.net/index.php?option=com_content&task=view&id=90&Itemid=61#pc_3 Gerard, In AppLogic when an appliance (virtual server) in a VPDC "goes down" it means something different than under a physical system. Data loss due to hardware failure is a very unlikely scenario under AppLogic since storage is RAIDed across multiple servers. Typically when an appliance goes down, the situation is one of: - out of resources (usually memory or disk) - software bug - intentional or unintentional deletion (including hacking) In the first two cases, you don't generally lose data. To fix resource issues (after determining they weren't caused by a bug), you change the resource allocation on the offending appliance and restart. This takes less than a minute typically. AppLogic has built-in monitoring that can warn of impending resource issues, so you can usually choose your downtime. In the case of a software bug, you fix the bug and restart, using a procedure similar to the one in the blog article. Again no data loss. So the interesting situation is if you're hacked or delete your data. AppLogic is not a substitute for a good backup strategy; however, you never need to use backup to restore broken hardware. In AppLogic, you replace the failed hardware and initiate a reintegration process, all of which occurs while your application is running. Because of the reliability of the AppLogic grid storage, backup consists at the minimum of simply instantiating another NAS appliance, or even a special directory in your existing NAS, and writing to it with backup software. Also, you can back up your entire application (all of the virtual servers, their configs, and their data) so you can restore a hacked site to a prior checkpoint in a couple minutes by restarting the backup. - e novikoff Fri, 04 Jan 2008 15:09:34 +0100 http://www.enkiconsulting.net/index.php?option=com_content&task=view&id=90&Itemid=61#pc_2 Very interesting article! How do you manage Data? For example if the MySQL instance goes down or you lose the NAS how do you "restore" in those type of scenarios? - Gerard Horan Thu, 03 Jan 2008 08:51:46 +0100