SSD’s in servers, best practice redundancy

That depends on the environment, and the disks you use. You're probably wanting to look at "Enterprise Flash Drives" rather than SSD. I would make the distinction as the longevity difference is significant.

This article discusses viability of EFDs in enterprise environments. This one discusses longevity of Seagate's "Pulsar" drive. According to Anandt's math, the 200TB version offers about 6 TB of writes before it fails, assuing 4k random read/write over 5 years. The smaller drives add up to less.

You may wish to check the comment string on Chopper 3's post in this question, he has a real world example that may be pertinent to you.

The long and short of it is that it depends on just how write-heavy your environment is. Remember that the wear on SSD/EFD drives is from writes not reads, so if people are just reading from your database, You could conceivably get 2-5 years out of your RAID.

You will get very good performance out of the raid. Switching from spinning disk to SSD has been the single most noticeable performance change in my home PC in the past two years.

I would consider a hybrid solution which could be achieved with OpenSolaris, SolarisExp 11, OpenIndiana, or Nexenta. Hybrid pool would be a lot less costly, and with a few thousand bucks worth of RAM, you will have your 150k+ IOPS with mostly normal spinning disks. At Nexenta we have many, many customers who do just exactly this. ZFS is a robust filesystem, and with enough RAM and/or SSDs for additional Read/Write caching you can have a very robust solution at a relatively low cost. With Nexenta Core, which is community, you get an 18TB at no cost at all. Of course, a new release of OpenIndiana would allow a lot of the same functionality. Add to this snapshots, cloning, replication usinf ZFS send/recv and you can build a SAN that will give any EMC a run for its money at a far lower cost. Lots of SSDs are nice, but there are other options, some not half-bad.