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The Computer Corner


By Charles Miller


Understanding Solid-State Computer Drives


Many new laptop computers are now being sold with Solid State Drives (SSD) in place of the traditional mechanical drives with motor and spinning disks. Once these SSDs were quite expensive, but prices have come down to the point that SSDs are commonplace in new laptop computers. Solid state is ideal for laptops and phones because these drives are not susceptible to damage from vibration or being bounced about.

Solid state drives are divided into two types: single-level cell (SLC) and multi-level cell (MLC). SLC is faster, much more reliable, and expensive. MLC is less reliable, less expensive, and often found in consumer-grade products such as smartphones, and USB memory sticks.

A common misconception is that a solid-state component with no motor and no moving parts is something that will never wear out. The reality is that solid-state components do in fact wear out; they just do so differently than mechanical parts. They all eventually fail, and they do so spontaneously with no warning.

One way to understand solid-state memory is to visualize a piece of blank paper. Every time you want to write a bit of data to the memory, you take a needle and poke a tiny hole in the sheet of paper. You can do this many thousands of times if you space your holes close together, but eventually you will run out of paper and have no place for any more new holes.

All flash memory suffers from wear. In technical terms, this happens because an electric charge is trapped in the transistor’s gate dielectric and causes a permanent shift in that cell’s characteristics, which, after a number of cycles ultimately manifests as a failed cell. Each cell of an MLC drive is typically rated at 10,000 write/erase cycles, while an SLC cell might go 100,000 cycles before failing. But it will still fail eventually! It is not a question of if, only when.

The old-style mechanical hard drives with motor and spinning disks were good about giving warnings before they failed. The drive would get sluggish, overheat, and even sometimes make strange noises. Any of this was warning of an impending failure. SSDs never do any of that. They work just fine up until the moment they die without warning. The manufacturers of memory chips have yet to come up with an accurate predictive failure model, except to know that Single-Level Cell (SLC) drives are more dependable than Multi-Level Cell (MLC) drives. This is what buyers of laptops should look for.

Recovering data from inside the chips of a solid-state drive is an expensive process that could cost thousands of dollars, so if you do not have a backup of your documents and photographs, you might as well say goodbye to that data. The best defensive strategies against this kind of data loss are to always make good backups or to replace your SSD once it is two or more years old and before it fails. I recommend doing both.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981, and now practically a full-time resident. He may be contacted at 044 415 101 8528 or email FAQ8 (at)


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