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Why Power Failures Can Always Lead To Data Loss
bigsmoke writes "So, all your servers run on RAID. You back up religiously. You're even sure that your backups are recoverable. But do you also need a UPS? According to Halfgaar (on Slashdot before to promote better Linux backup practices), yes, usually you do. He argues that despite technological advancements such as file system journaling, power failures can still cause data loss in most setups."
Ok, people who don't just read the executive summary knew this all along, but perhaps it's necessary that someone spells it out for the rest: Journaling and RAID do not prevent data loss in case of a power outage (and many more circumstances). If you know why, just skip the article. If you're wondering how you can lose data if you write everything to two disks and your filesystem guarantees its own consistency, then perhaps this is the wake up call that you need.
APC is the only UPS maker on the market that has at least spent some small effort so that their UPSs can be properly integrated with a Linux machine. I made the mistake of purchasing an Ultra UPS as it was cheaper than the APC.
"Thanks for all the money you paid to us. We've used it to buy off ISO among other things" -Microsoft
The typical small UPS system has some amount of surge protection built-in. But it's typically only good for at most a couple thousand joules. But then, if you get a spike that is big enough to blow a varister, you also get to buy a new ups.
A better solution is to put a "whole house" surge protector on the circuit-breaker panel. It protects everything, with a much higher number of joules. Five or six pounds of varisters can absorb a lot more shock than one ounce of varisters. They cost about $100, and can be found at most big hardware stores or electrical supply houses. That doesn't eliminate the need for a ups. It does protect the ups, along with the other equipment, from most voltage spikes.
Last year, lightning hit the power pole 20 feet from my house. We know where it hit because the pole caught fire. My next-door neighbors on both sides lost every single piece of electrical equipment -- not just computers, TV's, and stereos, but also fridge, microwave, water heater, and range. All of it was damaged beyond repair. We barely noticed the hit, except for the bright flash of light, and had no damage at all.
Are you sure your disks are in write-through mode? Have you checked? Brad Fitzpatrick (of LiveJournal, memcache, OpenID, etc. fame) discovered that many disks lie about being in write-through mode, and wrote a utility to check it.