I put an SSD in my home PC and use it as the C: drive for launching the OS and apps. Then I added spindle drives for data. I love the speed. It boots in about 30 secs and most of that time is POST. When I first investigated going to SSD I was a little concerned about barrier degradation and the loss of bits it causes. When I did the math I found the drive should be good for about 5-6 years. Well, I have never kept the same HD for that long so I finally figured out I was worried about nothing (isn't that typically the case!). If I had to design very rapid SAN access I would probably combine RAMDisk and SSD; RAMDisk for read/write intensive files/apps and SSD for read intensive.
Ramdisk for cache and SSD for storage and high Read... hmm interesting. So RamDisk would fill the role played by SSD of cache in many hybrid SANs/Drives today.
With decent backups for a single PC, the degredation shouldnt be too bad since as you said the useful life is less than actual life in many cases... disks get replaced for faster, shinier disks
Meh, SSDs are slow!
Down the road a few years from now?
For Tier 1 HPC storage I think/hope we'll have SANs built on HMC, stacked DRAM technology with InfiniBand interconnects for host and scaling connectivity.
As for Tier 2 storage, I believe SSDs will take over that sector as the choice storage technology for entry and mid level businesses.
After that, prices for DRAM storage will go down as soon as SSDs (by then - Tier 2 storage) become cheaper. Costs invloved in investemnts and implementation will drop, too, as everyone wants more compact, energy efficient, easily scalable and all important, better performing storage. It's a strong and sound technology that can evolve greatly with the right investments.
Mechanical drives will be phased out entirely since the technology has always been the number one drawback and or bottleneck in any system being built.
Until then, i think they'll serve a purpose in the now called "cloud" storage sector for low level capacity access for the masses ...until the governments decide that the disks are causing the polar ice caps to melt, forcing business to invest in a "greener" tech.