SATA-1 has been widely used, with a maximum data transfer rate of 150MBps and a signal line of up to 1 meter. SATA generally uses a point-to-point connection method, that is, one end is connected to the SATA interface on the motherboard, and the other end is directly connected to the hard disk. No other device can share this data line, and parallel ATA allows this situation (each data line can connect 1-2 device), so there is no need to set up a master disk and a slave disk like a parallel ATA hard disk. (As shown in Figure 1)
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| Figure 1 |
In addition, the hot-swappable function of SATA is unmatched by PATA. This function can make it more convenient to build a disk array. Since the serial port data cable only uses a four-pin structure, it is more convenient to install than the parallel port, which is more conducive to reducing the number of cables in the chassis and conducive to heat dissipation. (As shown in Figure 2)
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| Figure 2 |
SCSI
SCSI (Small Computer System Interface) is a storage unit interface mode specially designed for small computer systems. It can perform dynamic division of labor on multiple devices in the computer. It can flexibly and appropriately allocate multiple tasks required by the system at the same time. Completed dynamically.
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| Figure 3 |
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| Figure 4 |
SCSI hard disks also have an SCA2 interface (80-pin) that specifically supports hot-swappable technology. When used in conjunction with the SCSI backplane, hot-swappable hard disks can be easily realized. Hot-swappable functionality is now almost a must-have in workgroup and departmental servers.
SAS
SAS is the abbreviation of Serial Attached SCSI, that is, serial attached SCSI. On November 26, 2001, Compaq, IBM, LSI Logic, Maxtor and Seagate jointly announced the establishment of the SAS working group, whose goal is to define a new serial point-to-point enterprise-class storage device interface.
SAS technology introduces SAS expanders, which allow SAS systems to connect more devices. Each expander allows multiple ports to be connected, and each port can be connected to SAS devices, hosts, or other SAS expanders. In order to protect user investment, the SAS specification is also compatible with SATA, which makes the SAS backplane compatible with both SAS and SATA hard drives. For users, there is no need to reinvest when using different types of hard drives.
Currently, the SAS interface rate is 3Gbps, and most of its SAS expanders are 12 ports. Soon, high-speed interfaces of 6Gbps or even 12Gbps will appear, and 28- or 36-port SAS expanders will appear to adapt to different application needs.
Summarize:
Since SCSI has the advantages of low CPU usage, high efficiency of multi-task concurrent operations, many connected devices, and long connection distance, for most server applications, it is recommended to use SCSI hard drives and the latest Ultra320 SCSI controller; SATA hard drives also have Hot-swappable capabilities, and can have good scalability on the interface, such as using SCSI-SATA, FC-SATA conversion interface, and SATA port multiplier (Port Multiplier) in rack servers, making it Better flexibility than SCSI. For low-end small server applications, the latest SATA hard drives and controllers can be used.
After determining the interface and type of the hard drive, it is necessary to focus on the technical indicators that affect the performance of the hard drive mentioned above. Based on factors such as rotation speed, single disk capacity, average seek time, cache, etc., combined with the financial budget, select the most suitable cost-effective one. hard drive solution.