HP 349239-B21 Serial ATA technology, 2nd edition - Page 7
Port multipliers, Targets, SATA/SAS interoperability
UPC - 808736769419
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Port multipliers SATA port multipliers require host controllers that are port-multiplier-aware, such as SATA 1.5 Gb/s (with extensions) and SATA 3.0-Gb/s. Therefore, port multipliers are not compatible with original SATA 1.5 Gb/s controllers. However, port multipliers are compatible with SATA 1.5 Gb/s drives. Port multipliers can only link to SATA drives; they cannot link to another port multiplier. The extensions in SATA 3.0 Gb/s require updated operating system and driver support. SATA 1.5Gb/s devices (that support extensions) and SATA 3.0-Gb/s devices are backwards compatible with SATA 1.5-Gb/s controllers. Targets In a SATA domain, targets are limited to SATA hard drives, each with a single narrow-link port. SATA drives are available in non-hot plug 3.5-inch drives and hot plug 3.5-inch and 2.5-inch small form factor (SFF) drives. SFF SATA drives consume 70% less space and use considerably less power than the 3.5-inch drives. SFF drives allow systems to be designed to accommodate more drives per U (1.75 inches), thereby increasing the total system I/Os per second per U (IOPs/U). SATA/SAS interoperability The Serial Attached SCSI (SAS) architecture enables system designs that deploy both SAS and SATA devices.1 SAS supports the SATA Tunneling Protocol (STP), which allows SAS controllers to communicate with SATA devices through expanders. SAS and SATA devices share the same physical device connector, except for an extension within the notch on the SAS connector. This extension allows a SAS connector to accept SATA device connections, but it will not allow a SATA connector to accept SAS device connections. The SAS interface allows the flexibility to install SAS drives, SATA drives, or a mix of both SAS and SATA drives in the same enclosure. SAS and SATA devices share the same physical device connector, except for an extension within the notch on the SAS connector (Figure 8). This extension allows a SAS connector to accept SATA device connections, but it will not allow a SATA connector to accept SAS device connections. The use of SATA drives should be limited to low-workload, entry-level servers and multi-drive storage configurations, such as JBOD or RAID. SATA drives are not recommended in non-fault tolerant applications with high IOPs, mission-critical applications, or extreme environments with excessive vibration. SAS is the ideal solution for mission-critical enterprise storage applications that require higher reliability, performance, and scalability. Figure 8. SAS and SATA device connectors 1 For more information, refer to the technology brief, "Serial Attached SCSI technology," at www.hp.com/servers/technology. 7