Why is there ongoing concern about SSD reliability? I know of several vendors who have this concern, but more often than not, this worry is due to lack of experience and a lack of understanding about SSD. SSD reliability shouldn't be an issue anymore, especially if you are using enterprise-class memory.
First, not all SSD is the same as what you use in your digital camera. Don't blame the makers of SSD-based systems for loosing all those vacation photos that you forgot to copy over to your desktop before the compact flash inside your camera failed. Flash SSD comes in two flavors: MLC Multi-Level Cell and Single Level Cell. Single Level Cells, the type used in enterprise class SSD, don't pack as much data in to the same space but are substantially more reliable.
Also, there is a difference in the controller technology that goes on Flash-based SSD. Some are more resilient than others. As we discussed in our article "Pay Attention to Flash Controllers when Comparing SSD Systems." Flash controllers have the ability to wear-level the writes, making sure you get maximum life out of the FLASH SSD. The controller also handles data protection functions like ECC and chip level RAID functions. Controllers also make sure the cells on an SSD wear at a consistent rate.
In enterprise-class flash configurations, we have seen excellent reliability. Advanced controllers and use of SLC are a direct reason as to why. In fact, some companies are getting so good at the controller side, they believe they will be able to get acceptable reliability from MLC based systems and start introducing those as tier two SSD for enterprises. If you still have concerns, there is always DRAM-based SSD systems or caching appliances that use DRAM. DRAM, with technologies like ECC and IBM's ChipKill technology, have made DRAM-based systems incredibly reliable. Most vendors of DRAM-based systems claim failure rates that are way below anything that mechanical systems can achieve.
SSDs can fail, and you need a back-up system just like you need for mechanical systems, but it's inaccurate to say that SSDs are not as reliable as mechanical drives as long as you're using enterprise-class memory. There are challenges to wide-spread SSD adoption, but reliability of the systems is no longer one of them.
