Log in

No account? Create an account
Flash-only laptop: goodbye disk drives! - brad's life [entries|archive|friends|userinfo]
Brad Fitzpatrick

[ website | bradfitz.com ]
[ userinfo | livejournal userinfo ]
[ archive | journal archive ]

Flash-only laptop: goodbye disk drives! [May. 23rd, 2006|09:54 pm]
Brad Fitzpatrick

Yes, it's finally happening!

I've hated disks my whole life, and it's finally happening, they're finally dying!

The article does a disservice, though, noting that rotational drives' peak throughput is marginally higher. You never get peak throughput. A flash-based harddrive with zero seek latency will be so fucking fast it'll be unbelievable.

Can't wait.

From: (Anonymous)
2006-05-24 05:35 am (UTC)
read the comment section by morcheeba and weep:

(Reply) (Parent) (Thread)
From: jeffr
2006-05-24 06:02 am (UTC)
Er harddrives don't fail all at once either. They are constantly remapping bad sectors until they run out of free sectors for remapping. They are reasonably good at failure recovery. Except cheap ide disks which store the remapping information on the drive itself, which may then fail, leaving you with the original bad blocks.
(Reply) (Parent) (Thread)
[User Picture]From: scosol
2006-05-24 07:32 am (UTC)
that's pretty dope- so you just slowly run out of space?
i don't know the numbers for disks offhand but I wonder if the calculation makes sense, regarding how quickly you lose space
so which drives store the remapping stuff elsewhere?

i would just replicate the remapping data across different parts of the chip...

(Reply) (Parent) (Thread)
From: jeffr
2006-05-24 08:26 am (UTC)
The space is not addressable by the operating system. You slowly run out of 'extra' space. There are many other tricks that drives employ to recover bad data, and many that operating systems can do that they often don't.

For example: drives often have several levels of parity information. Only the quickest hardware computed parity is examined for larger transfers. If a transfer fails you can actually do block by block transfers to get the drive firmware to do more expensive checks that can recover from double-bit errors. Rewriting these blocks that have problems will then cause drive firmware to relocate the block if it believes it can no longer store data.

I believe some firmware will try to repair the existing block before relocating. Reading and writing multiple times to verify the data. These checks can actually hang the drive for a second or more as the onboard micros are quite slow and the calculations are very expensive.
(Reply) (Parent) (Thread)