Serial ATA technology, 4th edition

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Serial ATA technology

Technology brief, 4

edition

Introduction ......................................................................................................................................... 2

SATA devices and interoperability with SAS devices

................................................................................ 2

Initiators

.......................................................................................................................................... 2

Expanders

....................................................................................................................................... 3

Targets and their recommended uses

.................................................................................................. 3

Entry SATA disk drives

.................................................................................................................. 3

Midline SATA disk drives

.............................................................................................................. 3

Enterprise mainstream SATA SSDs

.................................................................................................. 3

SATA technology

................................................................................................................................. 3

Serial data transmission

.................................................................................................................... 4

Signal integrity

................................................................................................................................ 5

Connectors and cabling

.................................................................................................................... 5

SATA topologies

.................................................................................................................................. 6

Internal

........................................................................................................................................... 6

External

.......................................................................................................................................... 7

Conclusion

.......................................................................................................................................... 8

Appendix: SATA terminology

................................................................................................................ 9

For more information

.......................................................................................................................... 10

Summary of content (10 pages)

PAGE 1
Serial ATA technology Technology brief, 4th edition Introduction ......................................................................................................................................... 2 SATA devices and interoperability with SAS devices ................................................................................ 2 Initiators .......................................................................................................................................... 2 Expanders ..........
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Introduction Serial ATA (SATA) has evolved beyond a serial replacement for parallel ATA in desktop computers. SATA is now an alternate, lower cost solution for non mission-critical enterprise storage applications. SATA technology can provide adequate scalability and hot plug capability needed for server and network storage devices at the entry to midrange levels. The Serial ATA Revision 3.0 and 3.
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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.
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Serial data transmission Serial communication requires a serializer/deserializer (SerDes) to convert parallel data into a serial bit stream and vice versa (Figure 2). A SerDes contains these components: • A parallel digital interface • First-In-First-Out (FIFO) caches • 8 bit/10 bit (8b/10b) encoder and decoder • A serializer • A deserializer Figure 2: The SerDes core integrates 8b/10b coding and decoding logic. The 8b/10b encoder converts each 8-bit data byte to a 10-bit transmission character.
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support data packet retry because data packets can be very large (up to 8 KB) and the SATA interface would have to buffer them for re-transmission. Signal integrity Serial architectures encode (embed) the clock signals in the data stream, eliminating the parallel bus skew problem of aligning data and clock signals. Serial architectures reduce electrical noise because they have fewer data lines to switch simultaneously and the low voltage reduces the effects of capacitance, inductance, and noise.
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Figure 5: The SATA device connector is similar to the SAS device connector. You can connect SATA 6 Gb/s devices using the same cables and connectors as SATA 1.5 Gb/s and SATA 3 Gb/s devices. To maintain signal integrity of a SATA 6 Gb/s device requires high-quality cabling and connectors. SATA topologies You can use SATA and SAS drives in the same storage enclosure. SAS architectures can support internal and external configurations.
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Figure 6: Internal drives connect directly to a controller. External Figure 7 shows a topology for connecting a 4-lane-wide port on a controller to an external storage enclosure. This storage enclosure example contains an internal 36-port expander that supports cascading an additional enclosure in a 1+1 configuration. Figure 7: This external port topology can support cascading to an additional enclosure. Dual-path SATA implementations use a single-domain method of providing tolerance to cable failure.
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configuration connects a controller to the IO module at each end of a set of cascaded JBODs. Each JBOD contains a single expander, as shown in Figure 8. This configuration requires half as many IO modules and expanders as other redundant storage configurations, so it is more economical. HP dual-path enclosures support both SAS and SATA configurations. Dual-path SATA implementations do not provide the full redundancy of a dual-domain SAS solution.
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Appendix: SATA terminology Table 1: SATA terminology Term Definition Entry drives SATA drives that provide a basic level of reliability and performance for environments that are not mission critical. Expander A SAS device that functions as a switch to attach one or more initiators to one or more targets Frame Information Structure A FIS is a packet that may contain ATA register contents, data, control information, or other information.
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For more information Visit the URLs listed below if you need additional information. Resource description Web address SATA IO Web site www.sata-io.org “Serial Attached SCSI technologies and architectures” technology brief http://h20000.www2.hp.com/bc/docs/support/SupportMan ual/c01613420/c01613420.pdf HP ProLiant drives and data storage http://h18004.www1.hp.com/products/servers/proliantstora ge/drives-enclosures/index.html “Server drive technology” technology brief http://h20000.www2.hp.