I think you will be challenged to find a 1U device. The smallest arrays from the major vendors are generally at least 2U. NetApp offers the FAS2220 in a 2U form factor, supporting 6 or 12 internal SAS/SATA/SSD drives. This is a great low cost solution. Since you are considering SSDs, be sure to check out NetApp Flash pools. They help optimize the value of SSDs by positioning them as a read/write cache combined with additional HDDs. If your working dataset changes over time, Flash Pools are extremely valuable to help keep the hot data on the high cost SSDs and the cold data on the HDDs.