Serial ATA technology, 4th edition

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Expanders
Expanders connect SAS initiators with SAS and SATA targets. They receive commands and data in one port and
route them to another port based on the address of the target. Expanders allow multiple drives to connect to a single
initiator.
Targets and their recommended uses
SATA targets can be hard disk drives (HDD) or solid state drives (SSD), each with a single port, or optical disk
drives. We offer SATA HDD and SSD in 2.5-inch small form factor (SFF) and 3.5-inch large form factor (LFF), in both
hot plug and non-hot plug versions. Optical disk drives are available in half-height and slimline (9.5mm) form
factors.
We categorize server disk drives in three levels based on performance, reliability, and capacity: Entry, Midline,
and Enterprise. We offer SATA drives in Entry and Midline levels.
We categorize Enterprise SSDs as Value, Mainstream, and Performance. Today’s HP SATA SSDs are available as
Enterprise Mainstream storage devices.
Entry SATA disk drives
Entry-level SATA drives offer the lowest unit cost for server solutions in non mission-critical, low workload
environments. This includes boot drives and large-volume, low-cost implementations such as file-and-print and video.
Entry-level drives also provide economical storage for static web pages, Domain Name Systems (DNS), or firewalls.
Midline SATA disk drives
Economical HP SATA Midline drives offer reliability and performance for high capacity implementations that are not
mission-critical, for example external storage, backup, and archives.
Enterprise mainstream SATA SSDs
SSDs achieve high random-read performance by eliminating the seek time and rotational latency of traditional disk
drives. HP SSDs are also as reliable as current HP Enterprise disk drives. More important for some applications, our
server SSDs deliver this level of reliability under conditions that are unsuitable for traditional disk drives, including
environments exposed to greater shock and vibration.
Our SATA SSDs use multi-level cell (MLC) NAND flash technology and are suitable for environments with
constrained workloads and less than 100% duty cycle. The NAND flash memory used in SSDs has a limited life
cycle for writes. Advanced techniques such as wear leveling, the TRIM command (dependant on controller, driver,
and OS support), and capacity over-provisioning help overcome this limit.
SATA SSDs are best suited for read-intensive, high input/output operations per second (IOPS) environments (where
writes are 30% or less of the total IO load) and for applications that do not require large capacity RAID
configurations.
SATA technology
SATA architecture uses point-to-point connections that allow each drive to communicate with a host without waiting.
SATA uses low voltage differential (LVD) signaling to address the electrical interference and signal integrity issues of
parallel ATA. The LVD signaling scheme uses two pairs of data lines to transmit low-voltage signals between the host
port and the SATA device. The voltage potential between each wire pair represents a data bit. SATA technology
lets engineers shrink connectors, cabling, and device form factors while lowering power consumption.