About the 4x1 HPM Series
The 4X1 eSATA/USB Hardware Port Multiplier (HPM) is the first in Addonics HPM family with an integrated RAID controller for superior read/write performance. This 4X1 HPM can connect up to 4 SATA / SATA II hard drives to a host via a single SATA port or USB port. The 4 connected drives can be easily set to different RAID configurations by dialing an onboard rotary switch. There is no installation of driver or any software required, thus making the addition of RAID storage to any system simple no matter what the Operating System.
The RAID volume, once created, appears to any OS as another hard drive. It can be used as a boot drive in application servers or mission critical equipment. The flexibility and performance of this 4X1 HPM make it the ideal equipment in high capacity storage applications such as video storage, data archiving, home entertainment or multi-Tera bytes storage farm.
About the System Version (AD4SR5HPMUS)
The 4X1 eSATA/USB HPM comes in choice of the system version or the enclosure version. The system version enables multiple hard drives inside a system to be connected together to form a RAID volume. The enclosure version fits perfectly into the Addonics family of Storage Tower, Storage Rack and many standard multi-bay enclosures with standard SCSI-1 connector cut out. The 4 hard drives inside the drive enclosure, connecting to this HPM, can form a high performance and reliable external RAID system that can be attached to any computer via high speed eSATA or USB 2.0 ports.
For more detail information on Port Multiplier technology, please review the following URL link:
http://www.sata-io.org/technology/port_multipliers.asp
4x1 eSATA/USB Hardware PM System Version
(AD4SR5HPMUS)

Note:
1, drives connected to this PM cannot be configured as independent drive. All connected drives must be configured as 1 RAID volume.
2. BIG2 and BIG4 are capable of combining drives of different capacities, but the total combined capacity is limited to the number of drives multiplied by the capacity of the smallest drive.