NNSquad - Network Neutrality Squad
[ NNSquad ] Restoration of Gmail accounts from tape almost completed
Restoration of Gmail accounts from tape almost completed http://j.mp/hN0gYu (Official Gmail Blog) - - - A number of people have asked me about this incident, especially the "how could multiple copies of data be damaged/lost?" question. While I wouldn't assert that this example is strictly relevant in this particular case, RAID may provide a useful example. I've been warning folks for years that even the higher levels of RAID (Redundant Array of Independent Disks) protection do not necessarily mean that data won't be lost, especially when those disks all share a single controller. If the controller in such a situation fails in a particularly nasty way, it could potentially corrupt enough of the data across the entire array of RAID disks to cause unrecoverable data loss. Even when your redundant data is stored at different locations, it is possible for failure (in this case, likely a software-related problem) to cause data loss or corruption that may not be detected until it has been copied across to other replicated versions of the files. Even if you kept multiple copies of an email index, it's possible to have failure modes where problems in one copy spread to the other copies prior to detection. That's why having completely isolated backups -- such as tape in Google's case -- makes excellent sense. And for those of you attempting to use this case as an argument against cloud computing, I would simply note that only a relatively small number of Google's users were affected, it appears that their data will be successfully recovered, and when most people's home or business PC disks fail, they probably haven't been backed up at all. Technical term for that: S.O.L. --Lauren-- Lauren Weinstein (lauren@vortex.com): http://www.vortex.com/lauren Co-Founder: People For Internet Responsibility: http://www.pfir.org Founder: - Network Neutrality Squad: http://www.nnsquad.org - Global Coalition for Transparent Internet Performance: http://www.gctip.org - PRIVACY Forum: http://www.vortex.com Member: ACM Committee on Computers and Public Policy Blog: http://lauren.vortex.com Twitter: https://twitter.com/laurenweinstein Google Buzz: http://bit.ly/lauren-buzz Quora: http://www.quora.com/Lauren-Weinstein Tel: +1 (818) 225-2800 / Skype: vortex.com