RE: birding-aus Digest, Vol 48, Issue 5

Subject: RE: birding-aus Digest, Vol 48, Issue 5
From: Paul Taylor <>
Date: Wed, 03 Mar 2010 19:09:06 +1100
On 3/03/2010 5:47 PM, Chris Sanderson wrote:
Hey Dave, solid state hard drives, while expensive, have a very long shelf
life.  They are good because there are no moving parts at all, so less wear
and tear on the parts over time.  Something to look into for archiving
valuable data.  I saw a video of a guy throwing a laptop out of a second
story window, retrieving the hard drive (solid state one) from the wreckage
and plugging it into a new machine to demonstrate it still worked.  Not that
I recommend trying that at home, but it's definitely a promising technology.

It's true that solid state disks are more resistant to physical damage that hard disks but they use Flash memory and are prone to the same data corruption as Flash memory cards and
USB sticks.

It should also be noted that there are two types of Flash: SLC (single-level cell) and MLC (multi-level cell.) SLC stores one bit (i.e. 0 or 1) in each cell - it's either charged or not charged. MLC uses fractional charges e.g. no charge = 00, 1/3 = 01, 2/3 = 10, full = 11.

MLC is cheaper as more data can be stored in the same number of cells, but has a higher rate of data corruption - it's easier for a cell to change between the different charge states since they are closer together. MLC controller chips generally store more error correction data to compensate for higher error rate, but personally I would stick with SLC where possible.


   Paul Taylor                                  Veni, vidi, tici -
                           I came, I saw, I ticked.


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