SAS (Serial Attached SCSI) is Serial Attached SCSI. It is a new generation of SCSI technology. It is the same as the popular Serial ATA (SATA) hard disk. Both use serial technology to obtain higher transmission speed, and shorten the connection line. Improve interior space, etc. SAS is a new interface developed after the parallel SCSI interface. This interface is designed to improve the performance, availability and scalability of storage systems, and to provide compatibility with SATA hard drives. It can provide the high performance, high scalability and reliability required for mainstream servers and enterprise-class storage with higher bandwidth requirements. SAS addresses the need for high-frequency and immediate, random data access in transactional data application environments such as online shopping and banking transactions.
Design size
Previously, the mainstream desktop disks and server disks were designed with 3.5 inches, while SAS hard disks used a 2.5-inch reduced version in addition to the traditional 3.5-inch specifications, so that they can be installed in the limited space of rack-mounted servers. More disks can expand the capacity of the storage system, and can also make more space for other accessories for ventilation and heat dissipation. The use of 16 2.5-inch SAS hard drives within a 2U height has become the choice of most OEM server manufacturers.
Performance
The data throughput capacity of the first generation of SAS reached 3Gbps. In order to keep up with the increasing microprocessor speed and more and more advanced application requirements, the speed of subsequent generations will be gradually increased until 12Gbps. In addition, SAS uses multiple point-to-point connections to support fault-tolerant designs. The full-duplex, point-to-point design of SAS enables simultaneous active connections between multiple initiators and high-performance SAS target devices. Devices can transmit data in both directions at the same time, effectively doubling the available bandwidth of the link. Narrow ports allow single-lane serial links, while wide ports support multiple links for aggregate bandwidth to 8-lane SAS or SATA targets, increasing the total bandwidth to 24Gbps.
SAS is more useful for building large, high-performance topologies due to the use of more advanced cabling. SAS uses a thin 4-wire SAS cable. This compact design enhances airflow in the chassis and simplifies hot-plug connection of devices.
Flexibility
One of the key advantages of SAS is its backplane design and protocol interface, which allows the use of both SAS and SATA hard drives in the same system. While the two drives are typically used for different applications, many business users may need to use both. This ability to mix and match different types of drives will greatly benefit both system integrators and end users.
SATA drives are designed for cost-effective storage and tend to be used in applications where transaction processing is low and data availability is not a critical metric.
SAS drives, on the other hand, are designed for high-performance, high-reliability applications. SAS hard drives operate at higher rotational speeds (10,000 to 15,000 rpm) and are equipped with rotational vibration compensation to ensure data accuracy, so they have higher reliability. SAS hard drives will be used in applications where data availability is critical.
Since SATA connector signals are a subset of SAS signals, SATA hard drives are fully compatible with SAS controllers. This compatibility reduces the cost and complexity of storage designs and enables greater variety of design options.
SAS-SATA compatibility also allows system integrators to design hybrid storage systems using common connectors and cables. SAS backplane connector accepts both SAS and SATA hard drives for greater design flexibility.
Extensibility
The scalability of a parallel bus is limited due to its shared connection channels, and even increasing the number of buses through multiple initiators does not help extend this limited capacity. SAS uses expander hardware as its switching device to simplify the configuration of large external storage systems. This expander hardware enables flexible storage topologies with a mix of up to 16,256 SAS/SATA drives. The SAS expander hardware functions like a switch used to simplify the configuration of large systems. The system scales by minimizing latency, leaving bandwidth for increased workloads.
For example, a fan-out SAS expander can connect up to 128 devices, including servers (initiators), SAS/SATA hard drives, and other SAS edge expanders connected in narrow or wide chains. These additional edge expanders can also connect to other hosts and hard drives, providing additional connectivity nodes. The SCSI Management Protocol (SMP) contained in SAS is used to manage these point-to-point connections in the topology.
Reliability
The multi-host (initiators) model has long been adopted in enterprise computing environments, providing multiple hosts or host bus adapters (HBAs) -- or both -- to provide hard disk access, guaranteeing that in the event of a device failure can continue to access the data. However, using multiple hosts in a parallel technology configuration does not eliminate the single point of failure problem that can block hard disk access. With SAS, a high-availability system can be built with dual-ported hard drives, eliminating any single point of failure.
Another way to use SAS to improve the system's fault tolerance is to use expanders to connect multiple hard drives to multiple host servers, thereby maintaining concurrent operation of many hard drives. Commands are communicated down one link, and data is returned over a link on another connection, further increasing the fault tolerance of the system.
Using the capabilities of SAS expanders, combined with dual-port SAS hard drives and SATA hard drives with dual-port adapters, users can easily design redundant systems with maximum fault tolerance. The 2.5-inch dual-port SAS hard disk, together with the standard 3.5-inch hard disk, can realize a fully fault-tolerant system design, and can easily meet new technical challenges in applications with higher and higher computing density. This scalable and reliable connectivity fabric can be used to form enterprise-class topologies that support multi-node clusters, enabling automatic failover and load balancing critical in mission-critical applications.
Another key difference between SATA and SAS: Fees. Similar to ATA and SCSI, SATA and SAS disks differ greatly in price. SATA disks are cheap, while SAS disks are not. However, for attack-resistant storage and additional storage capabilities, many enterprises use SAS in the data center, which makes sense from the previous situation. Even though there are still some similarities between SATA and SAS, when comparing raw data center performance, SAS is the clear winner. SATA and SAS are very complementary technologies. SATA is especially suitable for desktop computers or for short-term storage, and it is also very suitable for internal storage needs of small businesses. On the other hand, SAS has taken over the banner of SCSI and has developed well in the enterprise field.
Send your message to us:
Post time: Aug-09-2022