There are still solid-state disk (SSD) devices around. Today, SSDs are typically packaged as storage subsystems that are rack mounted as opposed to having a disk drive form factor. Many different memory technologies have been tried but I believe most of them today use DRAM of some type with integrated battery backup.
Flash is less likely to be used due to the fact that flash cells are much slower to write to than standard memory and they have a limited lifetime. Read times for flash are faster than disk but write performance to flash and high speed rotating disk is relatively equivalent. In addition, flash cells can only be written to approximately 1 million times. This seems like a lot of writes but it isn't if you consider that SSDs are often used for transaction processing applications where the amount of writes can be high.
I have liked the idea of SSDs for a long time. The challenge is getting system software that knows how to make the best use of them. In a perfect world, the SSD memory could be used to accelerate any I/O constrained application on demand. Unfortunately, this is far more easier said than done, which means that they tend to be used only for high-throughput, mission critical applications where the performance of the SSD can be justified.
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This was first published in May 2003