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This article will explain in detail the three ways to implement storage virtualization. The editor thinks it is very practical, so I share it for you as a reference. I hope you can get something after reading this article.

There are three ways to realize storage virtualization: (1) host-based virtual storage, relying on agent or management software; (2) storage device-based virtualization, relying on storage modules that provide related functions; and (3) network-based virtual storage, it can be divided into interconnected device-based virtualization and router-based virtualization.

The most popular understanding of storage virtualization (Storage Virtualization) is the abstract representation of storage hardware resources. According to the virtualization object, there are three main ways to implement virtualized storage.

Host-based virtual storage

Host-based virtual storage relies on agents or management software, which are installed on one or more hosts to control and manage storage virtualization. Because the control software runs on the host, this will take up the processing time of the host. Therefore, the scalability of this method is poor, and the performance of the actual operation is not very good. A host-based approach can also affect the stability and security of the system, as it can lead to inadvertently unauthorized access to protected data.

This method requires proper control software to be installed on the host, so the failure of one host may affect the integrity of the data in the entire SAN system. Software-controlled storage virtualization may also bring unnecessary interoperability overhead due to the differences between software and hardware of different storage vendors, so the flexibility of this method is also poor. However, because no additional hardware is required, host-based virtualization is the easiest to implement and has the lowest device cost. Vendors using this method tend to become software vendors in the field of storage management, and they already have mature software products. These softwares can provide easy-to-use graphical interfaces for SAN management and virtualization, and have a good load balancing mechanism in host and small SAN structures. In this sense, host-based storage virtualization is a cost-effective method.

Storage device-based virtualization

The storage device-based approach to storage virtualization depends on enclosures that provide related functions. Without third-party virtual software, storage-based virtualization often provides only an incomplete storage virtualization solution. For SAN storage systems with multi-vendor storage devices, this method does not work very well. Functional modules that depend on storage vendors will exclude the use of JBODS (Just a Bunch of Disks) and simple storage devices in the system because these devices do not provide storage virtualization capabilities.

Of course, using this approach means eventually targeting a single storage vendor. The storage-based virtualization approach also has some advantages: it is easier to implement in the storage system, easy to coordinate with the devices of a particular storage vendor, so it is easier to manage, and it is transparent to both users and managers. However, we must note that the lack of sufficient software to support it makes the solution more difficult to customization and monitor.

Virtual storage based on network

1) Virtualization based on connected devices

If the method based on interconnected devices is symmetrical, then the control information and data walk on the same channel; if it is asymmetric, the control information and data walk on different paths. In a symmetrical way, interconnected devices may become a bottleneck, but multiple device management and load balancing mechanisms can alleviate the bottleneck. At the same time, in the multi-device management environment, when a device fails, it is easier to support the server to achieve failure replacement. "however, this results in multiple SAN islands because a device controls only the storage system to which it is connected." Asymmetric virtual storage is more scalable than symmetrical storage because the paths of data and control information are separate.

The virtualization approach based on interconnected devices can run on dedicated servers, using standard operating systems such as Windows, SunSolaris, Linux, or vendor-provided operating systems. This method runs in a standard operating system and has many advantages of the host-based method-easy to use and cheap equipment. Many device-based virtualization providers also provide additional functional modules to improve the overall performance of the system, which can achieve better performance and better functions than the standard operating system, but require higher hardware costs. However, the device-based approach also inherits some of the shortcomings of the host-based virtualization approach, because it still requires an agent software or host-based adapter running on the host. Any host failure or inappropriate host configuration can result in access to unprotected data. At the same time, interoperability between heterogeneous operating systems is still a problem.

2) Router-based virtualization

The router-based approach is to implement storage virtualization on the router firmware. Vendors also often provide additional software running on the host to further enhance storage management capabilities. In this method, the router is placed in the data channel from each host to the storage network to intercept any command in the network from the host to the storage system. Because the router potentially serves each host, most control modules exist in the firmware of the router, which has better performance and effectiveness than host-based and most interconnected device-based methods. Because it does not rely on the proxy server running on each host, this approach is more secure than the host-based or device-based approach.

When the router that connects the host to the storage network fails, it may still cause the data on the host to be inaccessible. However, only hosts connected to the failed router will be affected, and other hosts can still access the storage system through other routers. The redundancy of the router can support dynamic multipathing, which also provides a solution to the above failure problem. Because routers often act as a bridge for protocol conversion, router-based approaches can also provide interoperability between heterogeneous operating systems and multi-vendor storage environments.

This is the end of this article on "what are the three ways to implement storage virtualization?". I hope the above content can be helpful to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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