There are three types of electrical interfaces for 2.5-inch / 3.5-inch storage disks: PCIe, SAS and SATA, “In the past, the development of data center interconnection was actually driven by IEEE or OIF-CEI institutions or associations, and in fact today has changed significantly. Big data center operators like Amazon, Apple, Facebook, Google, and Microsoft are driving the technology, not necessarily waiting for standards to be completed, but for the user to dictate everything. As for the future performance of the PCIe SSD,SAS SSD and SATA SSD market, share a forecast made by Gartner for everyone’s reference and communication.
About PCIe
PCIe is undoubtedly the most popular transport bus standard, and it has been updated frequently in recent years: PCIe 3.0 is still the most popular, PCIe 4.0 is rising rapidly, PCIe 5.0 is about to meet you, PCIe 6.0 specification has been completed version 0.5, and provided to the members of the organization, will be released next year on schedule final official version.
Each edition of the PCIe specification goes through five different versions/stages:
Version 0.3: A preliminary concept that presents the key features and architecture of the new specification.
Version 0.5: An initial draft specification that identifies all aspects of the new architecture, incorporates feedback from organization members based on version 0.3, and incorporates new features requested by members plus new features.
Version 0.7: Complete draft, all aspects of the new specification are fully determined, and the electrical specification must also be verified by the test chip. No new features will be added after that.
Version 0.9: Final draft from which organization members can design and develop their own technologies and products.
Version 1.0: Final official release, public release.
In fact, after the release of version 0.5, manufacturers can already start designing test chips to prepare for subsequent work in advance.
PCIe 6.0 is no exception. When backward compatible with PCIe 5.0/4.0/3.0/2.0/1.0, the data rate or I/O bandwidth will double again to 64GT/s, and the actual unidirectional bandwidth of PCIe 6.0×1 is 8GB/s. PCIe 6.0×16 has 128GB/s in one direction and 256GB/s in both directions.
PCIe 6.0 will continue the 128b/130b encoding introduced in the PCIe 3.0 era, but add a new pulse amplitude modulation PAM4 to replace PCIe 5.0 NRZ, which can packet more data in a single channel in the same amount of time, as well as low latency forward error correction (FEC) and related mechanisms to improve bandwidth efficiency.
About SAS
Serial Attached SCSI interface (SAS), SAS is a new generation of SCSI technology, and the popular Serial ATA(SATA) hard disk is the same, are the use of serial technology to obtain higher transmission speed, and by shortening the connection line to improve the internal space. SAS is a new interface developed after the parallel SCSI interface. This interface is designed to improve the performance, availability, and scalability of the storage system, providing compatibility with SATA hard drives. The SAS interface not only looks similar to SATA, but is backward compatible with the SATA standard. The Backpanel of the SAS system can connect both dual-port, high-performance SAS drives and high-capacity, low-cost SATA drives. As a result, SAS drives and SATA drives can coexist in the same storage system. However, it should be noted that SATA systems are not SAS compatible, so SAS drives cannot be connected to SATA backplanes.
Compared with the great leap forward development of the PCIe specification in recent years, the SAS specification has gradually evolved quietly, and in November 2019, the SAS 4.1 specification using 24Gbps interface rate was officially released, and the next generation SAS 5.0 specification is also in preparation, which will further increase the interface rate to 56Gbps.
At present, in many new products, SAS interface SSD SSD is very few, an Internet user’s technical director said that Internet users rarely use SAS SSD, mainly because of cost performance reasons, SAS SSD between PCIe and SATA SSD, very embarrassing, performance can not be compared with PCIe. Ultra-large data centers choose PCIe, the price can not get SATA SSD, ordinary consumer customers choose SATA SSD.
About SATA
SATA is Serial ATA (Serial Advanced Technology Attachment), also known as Serial ATA, which is a hard disk interface specification jointly proposed by Intel, IBM, Dell, APT, Maxtor, and Seagate.
SATA interface uses 4 cables to transmit data, its structure is simple, Tx+, Tx- indicates the output differential data line, corresponding, Rx+, Rx- indicates the input differential data line, as the most widely used hard disk interface in the market, the current popular version is 3.0, the biggest advantage of SATA 3.0 interface should be mature, Ordinary 2.5-inch SSD and HDD hard disks use this interface, the theoretical transmission bandwidth of 6Gbps, although compared with the new interface of 10Gbps and 32Gbps bandwidth there is a certain gap, but the ordinary 2.5-inch SSD can meet the daily application needs of most users, 500MB/s or so read and write speed is enough.
Post time: Nov-10-2023
