Shulou(Shulou.com)06/02 Report--

By comparing SAN and NAS, one can understand what to consider when adopting these two storage system architectures. Object storage and cloud computing also affect the storage options available.

Storage area network (SAN) is storage connected in one structure, usually connected through a switch, so that many different servers can easily access the storage device. From a server application and operating system perspective, there is no significant difference between accessing data stores in SAN or directly connected storage. Storage area network (SAN), like direct attached storage (DAS), provides block access to data.

Network attached Storage (NAS) is a remote file service method. Instead of using software on the file system, it uses a remote protocol such as SMB or NFS to redirect file access to another device. The device runs as a server with its own file system, processes file Icano, and enables file sharing and centralized data management.

The decision between SAN and NAS usually boils down to the type of data stored by the user. When comparing SAN with NAS, keep in mind that NAS will eventually convert the file Imax O request into block access to the storage device attached to it. SAN is also the first choice for structured data, which resides in relational databases. Although NAS can handle structured data, it is often used for unstructured data, which consists mainly of files, e-mail, social media, images, video, communications, and almost any type of data outside relational databases.

The object ICompO used for storage has become more common, mainly due to its huge use in cloud storage. As a result, the obvious difference between SAN used with block storage and NAS with file storage becomes blurred.

When vendors move from blocks or files to object I _ peg O to meet their storage needs, users still want to access data in the way they are used to: block storage for SAN or file storage for NAS. The vendor-provided system has a front-end system that presents a NAS or SAN experience, while the back end is based on object storage.

File vs. Block vs object

The file Icano reads and writes data in the same way as the user on the drive on the computer, using a hierarchical structure, the files in the folder can be located in more folders. This approach is commonly used in NAS systems, and it has many benefits:

When using NFS and SMB, the most common NAS protocol, users can copy and paste files or entire folders like local and external drives.

The IT department can easily manage these systems.

Block I Pot O treats each file or folder as various blocks with smaller data bits, and distributes multiple copies of each block over various drives and devices in the SAN system. The benefits of this approach include:

Higher data reliability. If one or more drives fail, the data can still be accessed.

Faster access. Files can be reassembled from the block closest to the user without going through the folder hierarchy.

The object Imap O store treats each file as a single object, similar to the file Icano, and does not have a hierarchy of nested folders, such as block Icano. With object storage, all files or objects are placed in a large data pool or flat database. Find the file based on metadata that has been associated with the file or added by the object Storage operating system (OS).

Object storage is the slowest of the three methods and is mainly used for cloud file storage. However, the latest developments in the way metadata is accessed and the increased use of fast flash drives have narrowed the speed gap between objects, files, and blocks.

The use of NAS vs.SAN

The main difference between SAN and NAS is the impact of each type of storage on users.

NAS systems or devices are connected to the network through standard Ethernet, so they look like any other network-connected device to the user. The user connects to the NAS to access the files on it. The NAS device has an operating system that manages the writing and reading of any data requested by the user's computer.

Once it is installed on the user's computer, SAN appears as a local drive. This means that it will run as a local drive and the operating system on the user's computer will handle commands to read or write data. This allows users to treat it like any other local drive, including the ability to install software on it.

Connection of SAN vs.NAS

A NAS system can be a server or a set of drives or servers in a single device. This allows the NAS system to connect directly to the network, usually using an Ethernet cable connected to an Ethernet switch.

Instead, a SAN is a pool of drives, devices, or servers connected by a network structure, such as iSCSI or fibre Channel.

Ethernet and fiber optic networks have been competing on the basis of speed for many years. However, this advantage has always been reflected in the structure because it has a more direct connection and does not have to be handled through the TCP/IP of an Ethernet connection. In view of this, when the data speed is equal, the structure finally has the speed advantage of Istroke O, because when the data is transferred between the storage and the user, the number of data contacts is less.

Advantages of NAS

Ease of use is a key advantage of NAS. The metadata in NAS system is hierarchical and readable. Users can use a simple file system browser to view file names and organize them into folders that are easy to name.

With NAS, users can collaborate and share data, no matter where they are. NAS can easily access files and folders from any networked device.

NAS also provides high capacity at a lower cost than SAN. NAS devices consolidate storage into one place and support data management and protection tasks such as archiving, backup, and cloud storage. NAS can handle unstructured data, such as audio, video, websites, text files, and Microsoft Office documents.

NAS devices can be equipped with more or larger disks to expand storage capacity. This method is called magnifying NAS. They can also be gathered together for scale-out storage. High-end NAS devices can hold enough disks to support RAID.

NAS supports file access that is compatible with portable operating system interfaces, facilitates centralized management of security and file access, and ensures that multiple applications can share scale-out NAS devices without one application overwriting files being used by another application.

Shortcomings of NAS

NAS is not fast enough to meet the needs of high-performance applications. If too many users may crash the system while requesting the system at the same time, it may slow down further. However, in newer NAS systems, speed problems can be alleviated either in combination with HDD or as an all-flash system.

Scalability issues may occur with NAS. Adding too many NAS devices can lead to NAS contagion, especially if all devices must be managed separately. Clustering or scale-out NAS is designed to alleviate this problem.

Data integrity can be an issue because the file system stores metadata and file contents in logical or physical disk volumes. If the file server is powered off, the system must perform a file system check (also known as fsck) to verify the status of the data. Depending on the NAS system, the latency involved in performing a file system check (also known as fsck) can be large.

There may also be problems with NAS using RAID because RAID reaches the scalability limit. The rebuild time may take several days, which will only get worse as multi-TB capacity drives become more common.

Advantages of SAN

SAN treats raw storage as a pool of resources that IT can centrally manage and allocate as needed. Because SAN is connected through a network structure, data transfer and access using SAN is faster than NAS, all of which are true.

The SAN system is highly scalable. You can add capacity as needed. Other reasons for deploying SAN include continuous availability and resilience. High-availability SAN is designed to have no single point of failure, starting with high-availability SAN disk arrays and switches with redundant critical components and SAN redundant connections.

Shortcomings of SAN

Cost and complexity are the main disadvantages of SAN. The hardware of these systems is expensive, and building and managing them requires professional knowledge and skills.

SAN is much more complex than NAS and has dedicated cables, usually fibre Channel, but can use Ethernet, as well as private exchange and storage hardware. Optical fiber was developed specifically for storage because over the past decade, before protocol progress, Ethernet was not reliable enough to transmit data blocks. However, fibre Channel SAN requires expertise and dedicated connections.

Although SAN is highly scalable, the ability to scale up the SAN array vertically is limited. "once the upscale limit is reached, you must move to a higher-performance storage array or add multiple storage arrays." More and more SAN disk arrays avoid this problem by supporting scale-out, adding storage nodes that can scale capacity and performance at the same time.

How to adapt to DAS

DAS (direct attached storage) is a dedicated server or storage device that is not connected to the network. The simplest example of DAS is the hard disk of a computer. To access files on DAS, users must be able to access physical storage devices.

DAS can outperform NAS, especially for compute-intensive software programs. However, when using DAS, the storage on each device must be managed separately, which increases the complexity of system management. DAS systems typically do not provide the advanced storage management features common in SAN and NAS, such as replication, snapshots, and thin configurations.

DAS also cannot realize shared storage among multiple users. And because only one host accesses the DAS device, only part of the available storage ends up being used.

The rise of unified storage

The advent of unified storage gives storage administrators the flexibility to run blocks or files on the same array. These multiprotocol systems integrate data based on SAN blocks and data based on NAS files on one storage platform. Customers can start with SAN or NAS and add support and appropriate connections later. Or they can purchase storage arrays that support SAN and NAS.

Advantages and disadvantages of unified storage

Antony Adshead, editor of computer Weekly, talked with Andrew White, a former technical consultant at GlassHouse and now a consulting engineer at Dell EMC, about the challenges and benefits of unified storage.

Unified storage uses file and block protocols. It can use file protocols such as SMB and NFS and block protocols such as FC and iSCSI.

One advantage of these systems is that they require less hardware than traditional storage systems. Newer unified storage products are integrating cloud storage and storage virtualization.

The motherboard may give birth to the future

The biggest action and excitement today comes from extending the non-volatile memory (NVMe) protocol through the structure.

NVMe protocol is the fastest way to connect flash memory devices directly to the computer motherboard and communicate through the interconnection of peripheral components with high-speed buses. Its performance far exceeds that of SSD hard drives connected through SATA. Imagine what it would be like to integrate this fast NVMe connection across the entire SAN system.

To be fair, NVMe cannot be used to transfer data between remote end users and storage arrays, so a messaging layer must be used. This makes NVMe look more like an Ethernet-connected NAS system that uses Ethernet's TCP / IP protocol to handle data movement. But NVMe over Fabrics developers are working on using remote direct memory access (RDMA) to minimize the impact of this messaging layer on speed. Among the various types of RDMA proposed, there are RDMA on converged Ethernet, global Internet wide area RDMA protocol and InfiniBand, which are used in high performance computing systems.

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