With the increase of enterprise network application data volume, enterprises have felt that storage capacity and performance lag behind the development needs of network applications. The technology that satisfies the user's storage needs under this kind of application condition arises at the historic moment, the three kinds of storage technology of DAS, NAS and SAN become the mainstream storage technology of the present day.
According to the type of server, it is divided into closed system storage and open system storage, closed system mainly refers to mainframe, open system refers to servers based on Windows, UNIX, Linux and other operating systems; open system storage is divided into: built-in storage and external storage The external storage is divided into direct-attached storage (DAS) and networked storage (fabric-attached storage, FAS for short) according to the connection method. The networked storage is divided into: network access according to the transmission protocol. Storage-Network Attached Storage (NAS) and Storage Area Network (SAN).
DAS storage
DAS storage is very common in our lives, especially in the application of small and medium-sized enterprises, DAS is the most important application model, the storage system is directly connected to the application server, in the small and medium enterprises, many data applications must be installed On direct-attached DAS storage.
DAS storage more dependent on the server host operating system for data IO read and write and storage maintenance management, data backup and recovery requires the occupation of server host resources (including CPU, system IO, etc.), data flow needs to return the host to the server connected With tape drives (banks), data backup usually occupies 20-30% of server host resources. Therefore, the daily data backup of many enterprise users is often performed late at night or when the business system is not busy, so as not to affect the operation of normal business systems. The greater the amount of direct-attached storage, the longer backup and recovery time, and the greater the dependency and impact on the server hardware.
The connection channel between the direct-attached storage and the server host is usually connected by SCSI. As the processing capacity of the server CPU becomes stronger and the storage hard disk space becomes larger and larger, the number of hard disks in the array increases, and the SCSI channel will increase. Become an IO bottleneck; SCSI ID resources on the server host are limited, and SCSI channel connections that can be established are limited.
Regardless of direct-attached storage or expansion of server hosts, scaling from one server to a cluster of multiple servers or expansion of the storage array capacity will result in downtime of business systems, which will bring economic losses to the enterprise. It is unacceptable that the key business systems of the 7×24-hour service in banking, telecommunications, media, and other industries. And the direct-attached storage or server host upgrades can only be provided by the original equipment manufacturer, and are often limited by the original equipment manufacturer.
NAS storage
NAS storage is also commonly referred to as additional storage. As the name implies, storage devices are added to a group of computers through a standard network topology (such as Ethernet). NAS is a file-level storage method, and its focus is to help work groups and department-level agencies address the need to rapidly increase storage capacity. Nowadays, users use more NAS functions for document sharing, picture sharing, movie sharing, etc. With the development of cloud computing, some NAS vendors have also introduced cloud storage functions, which greatly facilitates the use of enterprises and individual users.
NAS products are truly plug-and-play products. NAS devices generally support multi-computer platforms. Users can access the same documents through network support protocols. Therefore, NAS devices can be used in hybrid Unix/Windows NT LANs without modification, and NAS applications are very flexible.
However, NAS has a key issue, which is bandwidth consumption during backup. Unlike a storage area network (SAN) that transfers backup data streams from the LAN, the NAS still uses the network for backup and recovery. One disadvantage of NAS is that it transfers storage transactions from the parallel SCSI connection to the network. This means that in addition to having to handle normal end-user transport streams, the LAN must also handle storage disk requests that include backup operations.
SAN storage
Storage area network, we can see from the name, this is connected to the storage array and server host through the Fibre Channel switch, and finally become a dedicated storage network. After more than ten years of historical development, the SAN has matured and has become a de facto standard in the industry (but the fiber switching technologies of various vendors are not exactly the same, and their servers and SAN storage have requirements for compatibility).
SANs provide an easy way to connect to existing LANs and support the widely used SCSI and IP protocols over the same physical channel. SANs are not limited by the current mainstream SCSI-based storage architecture. It is particularly important that with the explosive growth in storage capacity, SANs allow businesses to independently increase their storage capacity. The SAN's architecture allows any server to connect to any storage array so that the server can access the required data directly, regardless of where the data is placed. Because of the use of fiber interfaces, SANs also have higher bandwidth.
Because SAN solutions are stripping out storage from basic functions, running backup operations does not need to consider their impact on the overall performance of the network. SAN solutions also simplify management and centralized control, especially when all storage devices are clustered together. Finally, the fiber optic interface provides a connection length of 10 kilometers, which makes it very easy to physically separate storage that is not in the room.
Summary: Finally, it is summarized that DAS storage is generally used by small and medium-sized enterprises. It uses direct connection with computers, NAS storage is added to computers through Ethernet, and SAN storage uses FC interfaces to provide more performance storage. The main difference between NAS and NAS is reflected in the location of the operating system, as shown in the figure below.
Nowadays, with the advent of the mobile computing era, more unstructured data is generated. This is a challenge for both NAS and SAN. NAS+SAN will be the main storage solution in the future, which is currently the most popular unified storage. Since it is a centralized disk array, it supports host-level file-level data access over IP networks or block-level data access over SAN networks through fiber-optic protocols. Similarly, iSCSI is also a very general IP protocol, except that it provides block-level data access. This disk array is configured with a multi-port storage controller and a management interface that allows storage administrators to create storage pools or spaces on demand and provide them to host systems of different access types.
Unified storage system: The front-end host interface supports FC 8Gb, iSCSI 1Gb, and iSCSI 10Gb, and the back-end has SAS 6Gb hard disk expansion interfaces, which can support SAS, SATA hard disks, and SSD solid-state drives with excellent scalability. Realize the perfect integration of FC SAN and IP SAN and various storage media, effectively integrate the user's existing storage network architecture, and achieve unified deployment and centralized management of high-performance SAN networks to meet the dynamic needs of business and application changes. The host interface and hard disk interface adopt a modular design. The replacement of the host interface or hard disk expansion interface eliminates the need to replace the firmware, which greatly simplifies the difficulty and workload of upgrade and maintenance.
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