How reliable are Solid State Disks (SSDs)?
We have already had one or two customers tell us that after the failure of their hard disk drive (HDD) they have decided to purchase a solid state disk (SSD). Prices for SSDs are falling, whilst in recent months prices for HDDs have been increasing. That combined with the perception that SSDs are more reliable have allowed them to fall into favour.
However, it came as quite the surprise to one customer when his SSD had stopped functioning completely. This is typical for SSD drives. Unlike HDDs which can often have a slowly degrading performance to the the point of failure, SSDs tend to be working OK one day, then catastrophic failure the next.
Put in the most simple terms, SSDs are much like a giant usb memory stick. A usb memory stick typically has one or two NAND flash memory chips and a single controller chip. An SSD has multiple NAND Flash memory chips. For example the 120GB OCZ Vertex 2 SSD has a total of 16 Flash NAND chips and a single controller chip.
In the case of recovering data from Flash NAND technology it is necessary to dismount the memory chips and read them directly using specialised technology. Then the controller chip is emulated and folder and file structure is recreated. Needless to say it is not as easy to achieve good results as it might sound.
In this most recent case, the OCZ 120GB Vertex II, the controller chip is manufactured by the popular supplier “Sandforce“. These controller chips have shown excellent performance and are currently being used widely by a number of SSD manufacturers. Unfortunately the Sandforce SF-1200 series controllers encrypt the data stored on the Flash NAND chips. This means if the chips are removed all the data pulled from them directly is useless due to the 128bit AES encryption.
As such the options for recovering data from Sandforce based SSDs are very limited. The printed circuit board components can be tested to see if any other parts are at fault, and a reflow of the PCB can ensure there are no bad contacts between any of the components and the PCB. Otherwise it is a non-recoverable device. In the case CDR received this week a processor chip proved to be the fault. As such, do not think of SSDs as a safe storage method, and do continue to back up your data.