Differences between NAS and San

San is short for storage area network, that is, San is a network;
NAS is short for network attached storage, that is, NAS is a storage device;

Therefore, San and NAS are not in the same category, so they cannot be compared at all.

Why do many people compare San and NAs in the following two cases:

1. They compared whether the server is connected to a fabric network (SAN) or a storage device through an IP (LAN) network. The previous one is connected to a ray array, the next type of connected NAS device. In order to sell the device, you must say that is good and that is not good.
2. It indicates that San and NAS complement each other. For example, NAS uses the San network for storage.

Compare fabric networks with Ethernet networks:

Viewpoint 1: The fabric network performance is higher than that of the Ethernet due to the following reasons:
1. fabric is designed as a high-speed transmission network,
2. In fabric networks, there is no competition and no confirmation is required. The data transmission efficiency is high, and the maximum size of a town is 2112 bytes.
3. fabric is a smart network that automatically reroutes and trunking (multi-port binding, bandwidth up to 8 GB)
4. Data Transmission in the fabric network is a block operation. Therefore, you must have good support for the databases that can be read and written to the disk directly. NAS generally does not support databases.

opinion 2:
the FC network performance is good, and it is also a storage network. The performance of server connection to storage is even higher, so it is also necessary to provide external services, servers need to provide external services through the network, and your backend is faster and subject to front-end network restrictions.
the FC network uses a second network to transmit storage data. If you use the second IP network to access the NAS device, the efficiency will be greatly improved because there are few machines in the second network.
at present, the FC network bandwidth is 1 GB and 2 GB. Even though trunk can only reach 8 GB, 10 Gb of the World Wide Web has been developed and put into use.
FC networks claim high transmission efficiency. If the IP network uses a Cisco 0-interference switch and a high-performance gigabit ethernet card, the transmission performance is also high.
the inherent defect of FC is poor data sharing capability. If you want multiple machines to share a data volume, you must support software such as sanergy and cvfs, management information also needs to be transmitted over an IP network, and migration and other operations are not supported, resulting in poor performance.
NAS is designed for data sharing.

Many large databases do not support NAS devices, because in order to speed up Data Reading and Writing during data access, the database needs to directly manage disks in the same field. If there is an additional file system in the middle, this greatly reduces data access performance.
"Bare devices and files
Data Warehouse manufacturers recommend that bare devices be used as database storage because this allows the database to fully control I/O and can lock and concurrently process I/O to improve performance, however, these features require a price replacement. Bare devices are difficult to manage and usually require interference from system administrators because they require superuser permissions to manage them. In addition, management tools for bare devices are relatively primitive compared with file management tools.
Today, file system technology has eliminated differences in file-based and bare-device-based performance. You can use a file-based database without sacrificing performance.
The database that uses files as database storage improves system availability because it reduces the possibility of human errors and promotes some applications, such as regular backup.
To speed up recovery, the underlying database file system should be a log-type file system.
-Paul massiglia Veritas Software"

After reading the above, I believe that we will rarely use the Oracle device when creating a database.

However, although the database is based on a file system, it is not NAS, because NAS uses the file transfer protocol, that is, when the database is built on NAS, if you want to obtain a record, the entire data file needs to be transmitted (if the database does not change the data access mode)

Oracle Database 9.0 and later versions support the dafs protocol:

Dafs (Direct Access File System)

As a file system protocol, it can effectively reduce the computing pressure of the storage server and improve the performance of the storage system when there is a large or even excessive load.
The basic principle of dafs is to reduce and re-allocate CPU computing tasks by shrinking the data path when the server reads and writes files. It provides direct memory-to-memory transmission, so that data block replication does not need to go through the cpu Of the application server and file service, instead, it is directly transmitted in the buffer zone pre-mapped by two physical devices. That is to say, files can be directly transmitted from the application server memory to the storage server memory, instead of filling in a variety of system buffers and network receivers. In this way, the file I/O operations are accelerated, and the storage network traffic is reduced. At the same time, because the operating system has less intervention in file operations, the reduced processing capability is released for other tasks.

Dafs was proposed by netapp. Although it is good, it only has the Solaris platform version. That is to say, Sun servers and netapp NAS must be used for backup,

Ms also launched an SQL Server database that supports NAs.

However, although the database is based on a file system, it is not NAS, because NAS uses the file transfer protocol, that is, when the database is built on NAS, if you want to obtain a record, the entire data file needs to be transmitted (if the database does not change the data access mode)

San uses the optical fiber protocol, while NAS uses the TCP/IP protocol.
San is mostly used for relational databases, that is, block,
NAS is mostly used for file.
Simply put, NAS is using your existing network, and San is another network on your server.

San focuses more on scope and efficiency!
NAS focuses on sharing!