Hard drive protection [LWN.net]

Hard drive protection

Posted Oct 13, 2005 6:55 UTC (Thu) by lienha_r (guest, #29121)
In reply to: Hard drive protection by jwb
Parent article: Hard drive protection

The problem is that you need quite a few heuristics in order to determine if the laptop really is falling: the sensors generate a lot of noise and it is not trivial to determine what is exactly happening. Imagine you're in a train, which is a typical situation where the laptop often receives little bumps. Would you like the disk head to park every 2 seconds?

For the paging problem, a simple solution is to mlock() the user-space program (that problem was also raised on the LKML) and to nice() it to a negative value.

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Hard drive protection

Posted Oct 13, 2005 12:12 UTC (Thu) by smitty_one_each (subscriber, #28989) [Link]

Your point is a good one, but, if I was, say, Fujitsu, I'd be looking to develop a minimialist, embedded piece of hardware in the drive itself. Call it "Project Codpiece".
It would be a great way to differentiate a hard drive product in the market.
Once the idea catches on, motherboard makers can put such a device on their products, and integrate it with the BIOS, so that you get an interrupt to park hard drive and secure the power supply, as well.

Hard drive protection

Posted Oct 15, 2005 5:40 UTC (Sat) by dvdeug (subscriber, #10998) [Link]

There may be quite a few heuristics, but probably not more than a few k of code. I doubt a userspace heuristic could do a lot better then something built into the hard drive.

As for the train situation, a disk head parking every 2 seconds wouldn't completely kill performance, and I don't see any reason why a userspace demon would be better at handling this situation than an embedded chip. In fact, a embedded chip could probably freeze and unfreeze the disk faster than a userspace demon could, making even pathological situations run better with an embedded chip instead of a userspace demon.

Hard drive protection

Posted Oct 31, 2005 4:48 UTC (Mon) by syzygylwn (guest, #33471) [Link]

1) Yes Train (in my case boat) movements are very hard to differentiate from falling.

2) Yes, even heads parking every few seconds does severely impact performance.

3) The IBM windows drivers have this problem.

I have a Thinkpad T43. It has this active protection system. I took a month long sailing trip which my laptop joined me on. As you might imagine a sail boat very rarely gets large shocks, usualy its more of slow rolls. The laptop (even on the lowest sensativity setting) would park its head durring all but the most calm settings. The real problem is that these sensors have to detect the notebook falling off of a table and speeding towards the floor, before it hits, with enough time to park the heads for impact. This is no small trick. It works well in most other situations I've put it in, but then again I was most likely to drop it on the boat which is when I had to shut it off to get any work done.