SSD (solid state disks) drives
Buurst's SoftNAS supports the use of high-speed SSD drives, including the latest, affordable MLC drives comprised of flash NAND memory, which typically provide access times 100 times faster than physical disk drives (e.g., access times in the 0.1 millisecond range are common, with 300 MB/sec to 450 MB/sec transfer rate per drive). This equates to 40,000 to 50,000 or more IOPS (I/O per second).
SSD are excellent for use as both Read Cache and Write Log purposes, augmenting main memory with additional high-performance caching and logging storage. Note that write log devices can be configured as RAID 1 mirrors, so you have double protection against drive failures and data loss.
Some recommended drives include Crucial M4 series SSD, which are widely available and very affordable. The Crucial M4 512 GB drive shown below costs a few hundred dollars and provides very impressive throughput and extremely fast read access, and respectable write speed as well. These drives are now less than $1 per GB and are as much as 100 times faster than SAS drives. However, there is a short life expectancy for these drives - est. 3 to 5 years, depending upon how much write activity your workloads exhibit. If you have high-write workloads, SAS drives may be a better choice for long term high-performance storage. If you have read-intensive workloads, it's hard to beat SSD for high-performance and durability, especially at the price. Of course, SSD are an excellent choice for read cache - a use case for which they're hard to beat.
Lastly, SSD consume about 1/10th the power of spindle drives like SAS and SATA disks, so if low-power operation is an objective, SSD are a great solution.