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Solid State Drive Storage

How do SSDs wear out, and how does this make them less reliable than hard disk drives?

SSDs have no moving components, this distinguishes them from traditional electromechanical magnetic disks such as hard disk drives Hard disk drives (HDDs) or floppy disks, which contain spinning disks and a movable read/write head. This means that compared with electromechanical disks, SSDs are more resistant to physical shock, run quicker and run quietly  or even silently. However, while the price of SSDs has continued to decrease over the years the question of the life span of Data centre arrays is still an unknown quantity.

Most SSDs use NAND-based flash memory, which retains data without power, when we talk about the life span of SSD, this refers to the NAND flash substrate which can sustain a finite number of erase cycles before it becomes unusable. The process of writing and erasing data involves hitting the flash cell with a relatively large charge of electrical energy, this causes the semiconductor layer on the chip itself to degrade a minute amount which, over time, can increase byt-error rates. Dependant on the vendor these errors are corrected by use of software, but eventually the error correction code routines in the flash controller can't keep up with these errors and the flash cell becomes unreliable.

Hybrid drives or solid-state hybrid drives (SSHDs) combine the best features of both SSDs and HDDs in the same unit, typically a large hard disk drive and an SSD cache to improve performance of frequently accessed data.