2. Applications of DAS, NAS, and SAN in database storage

1. Hard Disk Interface Type 1. parallel interface or serial interface (1) parallel interface refers to the interface for parallel transmission, for example, there are 0 ~ 10 digits, with 10 transmission lines, each line only needs to transmit one digit. In theory, parallel transmission is very efficient, but due to physical reasons on the line, its transmission frequency cannot be too high, so the actual

1. Hard Disk Interface Type 1. parallel interface or serial interface (1) parallel interface refers to the interface for parallel transmission, for example, there are 0 ~ 10 digits, with 10 transmission lines, each line only needs to transmit one digit. In theory, parallel transmission is very efficient, but due to physical reasons on the line, its transmission frequency cannot be too high, so the actual

I. Hard Disk Interface Type
1. parallel interface or serial interface
(1) Parallel interfaces refer to interfaces for parallel transmission, for example, interfaces with 0 ~ 10 digits, with 10 transmission lines, each line only needs to transmit one digit.
Theoretically, parallel transmission is very efficient, but due to physical reasons on the line, the transmission frequency cannot be too high, so the actual transmission speed is not proportional to the degree of parallelism, or even worse.

(2) The serial interface refers to the serial transmission interface, which is also 0 ~ 9 10 digits. If one transmission line is used, it must be transmitted for 10 times and the Hong Kong virtual host can be used.
Theoretically, the serial transmission efficiency is not high, but the transmission speed can be very high due to its data accuracy and high frequency support.

(3) parallel connection lines and serial connection lines (IDE/SATA)

At present, most computer external interfaces are replaced by serial interfaces, such as USB, 1394, and COM. The external interface of the hard disk has been occupied by the serial interface (SATA/SAS.

2. Hard Disk Interface Type
There are two types of hard disk interface protocols/specifications: ATA and SCSI. A hard disk that uses some interface is called a XXX hard disk.

2.1 ATA interface protocol
(1) IDE Interface
The IDE interface is also called the Parallel ATA interface, that is, the Parallel ATA interface. Hard Disks with this interface were widely used in previous PCs.

(2) SATA interface
SATA (Serial ATA) interface, Serial ATA interface, this type of hard disk, the speed is usually not high, the capacity is large, the current PC or IOPS requirements are not too high storage use this interface hard disk.

(3) IDE and SATA Hard Drive Interface icons

2.2 SCSI interface protocol
(1) SCSI interface
Commonly referred to as SCSI, is a parallel interface, early computer peripherals (printers, scanners, etc.), also mostly use this interface. Currently, there are very few hard disks using this interface.

(2) SAS Interface
SAS (Serial SCSI) interface, Serial SCSI interface, this type of hard disk, high speed, high IOPS, suitable for OLTP system storage.
In addition, the SAS interface technology is compatible with SATA. That is to say, if there is a SAS interface on the motherboard, it can be connected to the SATA hard disk, but not vice versa. From the picture, SAS and SATA interfaces are similar.

Ii. Storage Solution
The so-called storage solution is to use a separate software and hardware to manage the disk/disk group for use by the host.
Currently, there are three plug-in storage solutions:
(1) Direct Connected Storage (DAS: Direct Attached Storage)
(2) Network Storage device (NAS: Network Attached Storage)
(3) Storage Network (SAN: Storage Area Network)
The hard disks used inside the storage solution are SATA/SAS. After serial/RAID, the system provides access interfaces to the host.

1. DAS
Direct connection to Storage (DAS: Direct Attached Storage) means to directly connect a Storage device to a computer through the SCSI interface or FC interface. DAS is not a network storage, because only the host it is attached to can access it.
That is to say, when a Server failure occurs, the data in the DAS storage device connected to the server cannot be accessed.

DAS device example:

2. NAS
Network Attached Storage (NAS) connects a Storage device to a group of computers through a standard Network topology (such as Ethernet. NAS has a file system and an IP address, which can be understood as a shared disk of a network neighbor.

NAS device example:

3. SAN
The Storage Area Network (SAN) currently has two types of SAN Storage: one is fc san Based on Fiber Channel; the second is Ethernet-Based ip scan (also known as iSCSI ).
Fc san connects to the host (HBA) through an optical fiber switch, that is, all hosts that can connect to the optical fiber switch can access this storage;
As storage shared on the Ethernet, iSCSI is more similar to NAS.

Fc san device example:

Ip san device example:

3. database storage applications
Comparison of the three storage solutions,

1. DAS
It can be used as a local plug-in hard disk, but now there is a lot of space for a single disk. If there is a few TB of space, you can simply insert the hard disk in the host, and no plug-in is required.

2. NAS
Due to its file system features, coupled with Ethernet network cable transmission, it is more like my computer-network neighbors-shared disk, Hong Kong space, access is also similar to: \ NAS01 \ BACKUP \ database_name.bak. It is used for file sharing, backup, and archiving, such as historical backup files of databases or remote backup files.