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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."
From TFA:
(DRAM needs to be refreshed constantly otherwise it will loose it's data)
Fly, little data! Be free!
Definitely maybe?
I don't know about you, but my servers run on the power of cotton candy and happy thoughts.
I don't know about you, but my servers run on the power of cotton candy and happy thoughts.
As a former sysadmin, I would think that any machine reliant on 'happy thoughts' would be the most crash-prone system in the history of computing.
Every year during my review, I just pray the words "slashdot.org" aren't mentioned.
One of the first things that will happen, is that the memory DIMMs will no longer be refreshed properly (DRAM needs to be refreshed constantly otherwise it will loose it's data) and very rapidly, the memory will contain only garbage. The hard drives and DMA controller however, will run a bit longer; so if data is being written to disk, the DMA controller will keep reading data from memory, but it has no idea that this data is corrupted.
However, we've recently seen that RAM holds state well enough to preserve crypto keys thru a power cycle. This has very scary implications: the RAM knows what's happening, and behaves differently (loses data immediately on power-off or remembers it for several seconds) in order to cause the most difficulty for the owner of the machine.
Not only are computer components intelligent and self-aware, they're also out to get us!
Yes. My first reaction upon reading the summary was.. "Duh?" What, did they have it plugged into the wall before that? A UPS becomes MORE critical, not less, as the cost of hardware (RAID arrays are expensive) goes up.
End of lesson. You may press the button.
Ok, now everyone has something to give to your kid for the sysadmin-in-traning class.
For the rest of us... back to work, nothing here you didn't learn your first year.
For the poster... Shame shame... Turn in your card.
Do not meddle in the affairs of sysadmins, for they are subtle, and quick to anger.
My servers run on Electricity but the RAID controller has battery backed up RAM so any cached data will persist a power failure and the disks are in writethrough mode.
I like this setup, but please. Tell me more about this cotton candy technology? Is it superior.
If there's clouds in your server room, your server's probably been slashdotted and is on fire!
mcgrew's razor: Never attribute to stupidity that which can be explained by greedy self-interest
I can offer you a Happy Thought UPS. It's a box of puppies. Be careful though, it only has 500 puppy Amps of capacity.
Your mom loves you and pays for the electricity. That doesn't mean that your servers run on love.
Except the server that runs http://youporn.com/
Paying taxes to buy civilization is like paying a hooker to buy love.
its not worth loosing you're cool about grammer misteaks and etc.
rewriting history since 2109
All you need to do is have the grid power feed some high wattage light bulbs. And near the light bulbs is some solar cells. The output from the solar cells is used to charge batteries which feed an inverter that actually powers the computer. Of course there is some power loss in the conversion process, and you need to have some (ok, a lot), of the input power to the system commited towards running a cooling unit to keep things at a reasonable temperature. But the resulting device provides clean power with no possibility of any surges getting thru to the protected equipment.
Of course, if you go to this level of trouble for your power source, then I'd also suggest opto-isolating all signal lines to and from the server. And enclose the server in a well grounded faraday cage. And it wouldn't be a bad idea to have a dedicated comm link to a duplicate server located else where. Preferably on a different tectonic plate.
I tried one of those. You gotta keep adding food to it or it stops working after a week or two. Starts stinking, too.
They wouldn't warranty it so I ended up putting a Triplite ISObar surge suppressor between it and the server in our test environment and it was in service for years after that.
Never trust any piece of equipment...
You mean like a Triplite ISObar surge suppressor?