A Mac consultant takes the Mac mini and Mountain Lion Server to new places of reliability with Redundant Array of Independent Servers (RAIS) architecture. He's pulled together a DIY package of hardware and third-party software that offer multiple layers of redundancy for Mac servers, now running Mountain Lion.
Redundant Array of Independent Servers using Mac minis appears to have been initially discussed at the Mac IT site AFP548 more than a year ago. As I mentioned in a post at the time, Alex Narvey, co-founder of Precursor Systems, a Winnipeg-based Mac consultancy, was testing Lion-based RAIS setups that took advantage of Thunderbolt and Target Disk Mode built into Mac mini.
Narvey recently moved his RAIS setup to Mountain Lion, which now includes a pair of SSD Mac minis connected via Target Disk Mode and FireWire, primary file storage via ThunderBolt on a 6TB Promise Pegasus Level 6 array, and backup with rotating sets of Thunderbolt backup drives. He has a PDF diagram here.
The pair of Mac mini servers are mirrored over Target Disk Mode using SoftRAID's SoftRAID 4.33. Navey said that unlike his previous Lion setup, this new package can boot with either Lion or Thunderbolt. But he's using "FireWire to isolate the mirror from the Promise Pegasus RAID array and the backup drives which will all be Thunderbolt interface."
He offers a very straightforward checklist, which includes creating a Recovery Disk on a USB key.
It's all very interesting and a great system for SMBs.