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by mechanical_fish
5478 days ago
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RAID is a cheap answer but it doesn't solve the same problems. RAID controllers fail. Motherboards fail. Power supplies fail. Connectivity or power to entire racks fails. Moreover, humans fail. RAID cannot save you from human error that corrupts the filesystem, for example. RAID is just a little too efficient at replicating changes from one drive to the other. There's a tradeoff between how up-to-date your mirror is and how much time you have to detect a problem on the primary and stop that problem from replicating to the slave; RAID is firmly parked on one edge of the space of solutions. And, as you have noticed, RAID also cannot help you deploy your new code on one machine at a time, secure in the knowledge that you can fail over to the other machine in case of big trouble. (That doesn't work for every deployment, but it sure is a handy option when you need it.) |
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