SATA & eSATA General Overview
SATA is the next -generation internal storage interconnect, designed to replace parallel ATA technology. SATA is the proactive evolution of the ATA interface from a parallel bus to a serial bus architecture. This architecture overcomes the electrical constraints that increasrf the difficulty of continued speed enhancements for the classic parallel ATA bus.
Initially SATA was designed as an internal or inside-the-box interface technology, bringing improved performance and new features to internal PC or consumer storage. Creative designers quickly realized the innovative interface could reliably be expanded outside the PC, bringing the same performance and features to external storage needs instead of relying on USB or 1394 interfaces. Called external SATA or eSATA, customers can now utilize shielded cable lengths up to 2 meters outside the PC to take advantage of the benefits the SATA interface brings to storage. SATA is now out of the box as an external standard, with specifically defined cables, connectors, and signal requirements released as new standards in mid-2004. eSATA provides more performance than existing solutions and is hot pluggable.
SATA-II now offers performance as high as 3.0 Gbit/sec per device with the current specification. SATA uses only 4 signal lines, allowing for much more compact (improving internal airflow) cables compared with PATA. It also offers new features such as hot-swapping and native command queuing. There is a special connector (eSATA) specified for external devices, and an optionally implemented provision for clips on internal connectors.
Port Multiplier (PM)
Port multiplier devices are SATA-only based storage products and operate at 3Gb/s per ESATA port. A Port multiplier processor allows a single active host connection to communicate with multiple drives-up to five drives per PM port. They allow easy, cost-effective storage scalability both inside and outside the computer with standard SATA-II drives.
Additional controllers are no longer necessarily needed to expand storage. In-box cabling is greatly simplified with fewer cables attached to more drives. Port multipliers allow significantly higher performance in external storage than either USB 2.0 or Firewire.SATA PM requires that controllers support either command-based switching or FIS (Frame Information Structure)-based switching in order to use port multiplication.
Multi-Lane (SAS & SATA)
The Multi-lane SA/SATA cable & connection system is a fast, secure, simple, and clutter free design that greatly reduces the number of cables needed to connect controllers, backplanes, and standard SAS/SATA drives. It combines the RAID controller’s multiple SAS/SATA ports into single professional locking connections.Multiple 3Gb/s lanes of SAS/SATA traffic travel through just one cable from the RAID controller to the system backplane or to multiple hard drives with a breakout cable. Applications range from SAS high-end enterprise storage equipment to SATA low-end internal storage equipment.
Multi-Lane SAS/SATA-protocol interconnects are found in mainstream data centers and sub systems which require scalability, performance, reliability and manageability. SATA-protocol interconnects are targeted for the desktop, connecting the host system to peripherals such as hard drives and RAID arrays.
Fibre Channel is a technology for transmitting data between computer devices at high-speed data rates. Fibre Channel is especially suited for connecting computer servers to shared storage devices and for interconnecting storage controllers and drives. Fibre Channel works equally well for storage, networks, video and other applications. Since Fibre Channel is three times as fast, it has begun to replace the Small Computer System Interface (SCSI) as the transmission interface between servers and clustered storage devices. Fibre channel is more flexible; devices can be as far as ten kilometers (about six miles) apart if optical fiber is used as the physical medium. Optical fiber is not required for shorter distances, however, because Fibre Channel also works using coaxial cable and ordinary telephone twisted pair.
In computing, iSCSI is Internet SCSI (Small Computer System Interface), an Internet Protocol (IP)-based storage networking standard for linking data storage facilities. By carrying SCSI commands over IP networks, iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. iSCSI can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval. It is a popular Storage Area Network (SAN) protocol, allowing organizations to consolidate storage into data center storage arrays while providing hosts (such as database and web servers) with the illusion of locally-attached disks. Unlike traditional Fibre Channel, which requires special-purpose cabling, iSCSI can be run over long distances using existing network infrastructure.
iSCSI uses TCP/IP. In essence, iSCSI simply allows two hosts to negotiate and then exchange SCSI commands using IP networks. By doing this, iSCSI takes a popular high-performance local storage bus and emulates it over wide-area networks, creating a storage area network (SAN). Unlike some SAN protocols, iSCSI requires no dedicated cabling; it can be run over existing switching and IP infrastructure. As a result, iSCSI is often seen as a low-cost alternative to Fibre Channel, which requires dedicated infrastructure.
The Small Computer System Interface is a high-speed, intelligent peripheral I/O bus with a device independent protocol. It allows different peripheral devices and hosts to be interconnected on the same bus. Depending on the type of SCSI, you may have up to 8 or 16 devices connected to the SCSI bus. The number of devices can be dramatically expanded by the use of LUNs (Logic Unit Numbers). There must be at least one initiator (usually a host) and one target (a peripheral device) on a bus. There is a large variety of peripheral devices available for SCSI, including hard disk drives, floppy drives, CDs, optical storage devices, tape drives, printers and scanners to name a few. There are many implementations of SCSI starting with SCSI-1 to SCSI-2 to SCSI-3 including, Narrow, Wide, Fast, Ultra, Ultra-2, Ultra160 and Ultra320 SCSI.