Serial ATA II Spec Nears Completion
The Serial ATA II Working Group released three more specifications for SATA II at the Intel Developer Forum this week, leaving only two to go until the standard is complete.
The completed specs – Digital, Port Multiplier, and Port Selector – address reliability and connectivity issues for the next-generation serial storage interface.
Knut Grimsrud, Serial ATA II Working Group chairman and Intel senior principal engineer, reports the SATA II effort is focused on expanding the base Serial ATA 1.0 capabilities to address additional market segments, including the server and networked storage markets. The new capabilities will also benefit mainstream and high-end PC segments, Grimstud adds.
The Port Selector specification provides an alternate path to storage devices and makes it possible to build Serial ATA solutions with no single point of failure, according to Grimsrud. The spec is targeted at RAID, NAS, and disk-to-disk backup manufacturers that are developing fully-redundant storage topologies.
The updated Port Multiplier specification gives efficient connectivity to a greater number of devices through the use of a simple hub for port expansion, reducing the cabling burden and improving airflow in SATA storage subsystems. The Port Multiplier 1.1 specification adds the asynchronous notification scheme from the Digital 1.1 specification. This scheme allows Port Multipliers to notify the host if a device has been plugged or unplugged from a port, eliminating the process of host polling to determine where devices have been added or removed.
The Serial ATA II Extensions specification, also updated, defines native command queuing to increase performance in multi-threaded environments, and adds manageability, backplane signaling, and a few other storage subsystem-focused features, reports Grimsrud.
There are two specifications still under development that have not yet been released. The first is a second volume of the cables and connectors specification that defines new interconnect solutions, including external cabling solutions and multi-lane cable solutions. The second is the second-generation signaling (Phy) specification, which defines the details of the 3Gbps signaling rate that doubles the first-generation SATA rate.
Both of these are on track for completion near the end of the year, Grimsrud says.
QLogic, Emulex Embrace PCI Express
Also at the Intel Developer Forum, QLogic and Emulex, the dominant Fibre Channel host bus adapter (HBA) vendors, embraced PCI Express, the next-generation interconnect architecture developed by Intel and others.
PCI Express complements legacy PCI installations and uses serial technology to enable data to move at faster rates than PCI connections. PCI Express utilizes a 2.5-Ghz signaling rate with scaling performance up to 8 Gbps, which works well with next-generation 4 Gbps and 10 Gbps Fibre Channel technologies. Additionally, it also ensures HBA compatibility when servers begin shipping with PCI Express slots next year.
QLogic SANblade PCI Express HBAs are expected to be available later this year.
The Emulex LP10000Ex PCI Express HBA is designed for use with servers based on the PCI Express architecture and is software-compatible with existing PCI and PCI-X systems, according to Emulex. It is based on Emulex's Thor ASIC technology, which delivers more than 100,000 I/Os per second and 790 Mbps throughput across two ports.
The first PCI Express HBAs will run at 2 Gbps speeds, the companies announced.
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