Flash more reliable than hard disk?

Andrew Ku has an interesting article at Tom's Hardware showing that, despite claims by the vendors, the evidence so far available as to the reliability of flash-based SSDs in the field shows that they fail at rates comparable with hard drives. These failures have nothing to do with the limited write lifetime of flash, these are enterprise SSDs which have been in service a year or two and are thus nowhere close to their write life.

Although it is easy to believe that SSDs' lack of moving parts should make them more reliable, these results are not surprising:

• Experience shows that vendors tend to exaggerate the reliability of their products.
• Root-cause analysis of failures in hard-drive systems shows that 45-75% of failures are not due to the disks themselves, so that even if SSDs were a lot more reliable that hard drives but were used in similar systems, the effect on overall system reliability would be small. In fact, most of the SSDs surveyed were used in hybrid systems alongside disks.
• The flash SSDs have even more software embedded in them than disk drives. Thus even if their raw storage of bits was more reliable than the disk platters, they would be more vulnerable to software errors.

These are early days for the kinds of mass deployments of SSDs that can generate useful data on field reliability, so there is no suggestion that they should be avoided. The article concludes:

The only definitive conclusion we can reach right now is that you should take any claim of reliability from an SSD vendor with a grain of salt.