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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.
if only there was some sort of law that covered the tendency of things that can go wrong to go wrong.
I hear Murphy might have one :)
Jumpstart the tartan drive.
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
"3.2. (Ecrypted) file systems"
Please tell me more about these ecrypted file systems. Do they also do gurnalling?
Intron: the portion of DNA which expresses nothing useful.
The scary thing is that yet one more person can't feakin' tell the difference between "loose" and "lose." It's becoming an epidemic.
Don't disappoint your bird dog. Go to the range.
We just need to get that guy that declared Pluto is no longer a planet to declare that electricity no longer causes data loss.
Side note: He also declared that north is no longer a direction, blue is no longer a color, and your sister is no longer a virgin.
Paying taxes to buy civilization is like paying a hooker to buy love.
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.
...If you're a Mac fanboy running a network of Apple computers. If anything goes wrong, it's an artistic expression and anyone who criticizes the problem is a closed-minded square who "doesn't get it." Then you sit back in self satisfaction listening to alternative pop, thinking about how hip and different and enlightened you are.
Happy thoughts power supply: Dead stable.
Linux networks can run on happy thoughts as well as long as you run on electricity during the setup and installation stages and then switch to happy thoughts once everything's running properly...you just have to make sure you never, ever run emacs, vi, or Gpaint.
"When information is power, privacy is freedom" - Jah-Wren Ryel
Except the server that runs http://youporn.com/
Paying taxes to buy civilization is like paying a hooker to buy love.
You do now.
True confidence comes not from realising you are as good as your peers, but that your peers are as bad as you are.
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?