Friday, June 3, 2011

Solid State devices

Many products are deemed to be dead long before they eventualy die entirely.  Magnetic tape for datya storage is one, but there is a very important market for tape, though for the home user and small business, disk back up is now a much more viable proposition.  The next prediction is the death of the rotating hard drive.

We are all used to solid state memory for cameras, telephones and many video devices.  The capacity keeps increasing, and cost keeps coming down.  Just starting to come in are solid state drives for laptops and desk top computers.  As there is no head seek time, or rotational delay, reading can be very fast and many users are added them as the system drive in a  PC.  They report impressive performance in boot up and launching programs.  It is noit all good news, as writing can be slow, and there is an issue of limited write cycles.  Basically, sector will wear out if used too often.  The solution to the last point is that chip controllers use a feature called wear leveling, so when a sector has been used too many times, it will be physically moved to another location, while still keeping the same logical address.

Data recovery of such SSDs has two main problems.  If the controller dies, then it is necessary to work with the chips directly.  These means they have to be unsoldered from the board and read.  This means pointing a hot air gun at the chips and removing them, with out damage or over heating.  It is possible, and not quite as bad as it sounds.  The major problem though comes next.  Manufacturers do not publish their wear leveling routines.  As the chips are not meant to moved between devices, there is no requirement for any standards - all that matters is that when a sector number is requested, the correct data is returned.  The physical sector is not relevant in any way.

CnW are now looking at such drives, and memory chips and will be developing tools to assist with recovery