Promise Pegasus J4 Thunderbolt: Performance with Four OWC 6G SSDs and Incompressible Data

Some types of data cannot be compressed, and all varieties of SSDs with Sandforce controllers drop in write performance with incompressible data (read performance is unaffected in any meaningful way). Since reads dominate most computing scenarios, the write speed is generally much less important, so long as it is still reasonably fast (which it is here).

Still, for those looking for peak performance with any type of data, testing the worst case scenario (an absurdly unfriendly non-repeating random data stream) gives insight into the very worst case, which is unlikely to occure in most real world usage.

Performance with 1/2/3/4 SSDs on incompressible data.

Tested with diglloydTools DiskTester.

RAID-0 stripes of 2/3/4 SSDs + single SSD
(Data from diglloydTools DiskTester data graphed from fill-volume test)