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2012-11-15 12:57:43
SAS2008
PCI Express to 8-Port 6Gb/s SAS/SATA Controller 即提供了PCI和SAS协议。
应用场合
1： Direct Attached SAS/SATA controller solutions for entry to mid-range servers
2： Blade Servers:
3： External storage controllers requiring SAS/SATA interface for the host or drive side connect
特点如下：
内部集成了RAID可以支持RAID0
8 port SAS/SATA controller 即eight SAS/SATA phys
Supports 1.5Gb/s, 3Gb/s, and 6Gb/s SAS and SATA data transfer rates
Supports SSP, SMP, STP and SATA protocols
SAS and SATA device support
从上的图可以知道，SAS2008提供了双向的接口，向上提供PCI接口，向下提供SAS/SATA接口。一定程度上面实现了，数据的转化。
The LSISAS2008 controller supports the PCI Express Specification, Revision 2.0; the Working Draft of the Serial Attached SCSI-2 Standard; and the Serial ATA Specification, Revision 2.6 (15-February-2007). The PCI Express software is backward compatible with previous revisions of the PCI bus and PCI-X bus.
上面的图中扩展了 2008，加了expander，基本上已经构成了一个存储架构的一部分。在加上主CPU，x86,mips,powerpc就可以组成一个完整的存储系 统。我们可以知道SAS2008提供了8个SAS Port，可以使用其中几个来连接SAS Expander，将其余的SAS Port
用于扩展，用来连接JBOD。在图中的8个PCI用来连接主CPU。因此SAS2008就会涉及到对PCI配置空间的设置。
对PCI的支持
The LSISAS2008 controller supports the
PCI Express Specification, Revision 2.0. PCI Express software is
backward compatible with previous revisions of the PCI bus and PCI-X
bus. PCI Express is ideally suited for applications
in mobile, desktop, workstation,
server, embedded computing, and communication platforms.
Fusion-MPT architecture is a multithreaded I/O algorithm that supports data transfers between the host system and SAS/SATA devices. The Fusion-MPT architecture is a performance-based, message passing protocol that offloads the host CPU by completely managing all I/Os and minimizes system bus overhead. SAS2008中使用的是MPT来进行数据的通信与传输。
对SAS的支持
SAS is a serial, point-to-point, enterprise-level device interface that leverages the proven SCSI protocol set. SAS is a convergence of the advantages of SATA, SCSI, and Fibre Channel, and is the future mainstay of the enterprise and high-end workstation storage markets. SAS offers a higher bandwidth per pin than parallel SCSI and improves signal and data integrity.
The LSISAS2008 controller can function as an SSP initiator, an SSP target, an SMP initiator, an STP initiator, or a SATA initiator.The controller uses SSP to communicate with other SAS devices and uses SMP to communicate topology management information with other SAS devices. STP communicates with SATA devices by tunneling through SAS expanders to the SATA device or by using the SATA protocol to communicate directly with the SATA device .
Benefits of Fusion-MPTArchitecture
The Fusion-MPT architecture provides an
open architecture that is ideal for the SAS and SATA interfaces. The I/O
interface is interchangeable at the system and application level;
embedded software uses the same device interface
for different bus
implementations, just as application software uses the same storage management interfaces for different bus implementations.
The LSISAS2008 controller provideseight SAS/SATA phys. Each phy can form one side of the physical link in a connection with a phy on a different SAS/SATA device. The physical link contains four wires that form two differential signal pairs.One differential pair transmits signals, whilethe other differential pair receives signals. Both differential pairs operate simultaneously and allow concurrent data transmission in both the receive and the transmit directions
上面的图可知，每一个phy具有俩个差分对，分别用来接收和发送数据用。
SAS2008直接俩种类型的SASPort：wide port 和narrow port，其区别如下：
Phys are contained within ports. A port can contain a single phy or multiple phys. A narrow port contains a single phy, and a wide port contains two or more phys. The LSISAS2008 controller supports wide ports that contain up to eight phys. Because each phy within a wide port can transmit data at 6Gb/s SAS, increasing the number of phys in a port increases the data transfer rate. When eight phys are combined into a wideport a bandwidth of up to 48.0 Gb/s is possible.A link between two narrow ports is a narrow link. A link between two wide ports is a wide link. The following figure shows a narrow link and a wide link. The wide link in the example contains four phys in each port. Wide links can contain up to eight phys in each port.
上图说明了narrow port和wide port的不同，在一个Port中连接Phy的个数不同。在SAS2008中每一个Port最多可以连接8个phy。Each phy on the LSISAS2008 controller can function as an SSP initiator, an SSP target, an SMP initiator, an STP initiator, or a SATA initiator. A phy can function in only one role during a connection but function in different roles during different connections.The controller uses SSP to communicate with other SAS devices and uses SMP to communicate management information with other SAS devices. STP communicates with SATA devices in a SAS domain by tunneling through SAS expanders to the SATA device. The LSISAS2008 controller can also use SATA to communicate with other SATA devices.
SAS2008中的PCI寄存器
configuration registers
其中对每一个字节的说明，可以参考PCI2.2规范。
SAS2008中PCI Express Signals和6Gb/s SAS Signals。
上图中主要关注的是：PCE_RX和PCI_TX信号。
