Chapter II Network Storage Basic Concept
In a traditional network, the server and client are connected via the network, and the data is stored on the storage device belled in the server itself. When the customer requests, the data is transmitted to the client through the network. This puts a considerable requirement for the server. Since the server can only come with the local storage device, and the number of interfaces is limited, the number of storage devices that it can have is limited, thereby determining the amount of data that can be stored. It is limited. At the same time, the server must handle data search, management, including a series of jobs, requiring the server to have strong data processing capabilities. These inevitable results have increased the cost of the server.
2.1 from the server to the network
Above we discussed all the limits of simple client / server patterns. Here, we propose the concept of network storage. The easiest way, we are to move the storage from the server to the network itself. There are currently two industrial programs to support cross-network storage: NAS and SAN, which will give a detailed description of several network storage schemes.
2.2 NAS
Lan
NAS
NAS
Host
Host
DISK
DISK
NAS (Network Attached Storage), network attached
Storage, NAS is directly attached to TCP / IP networks (LAN or
WAN), access via CIFS or NFS. These 2 associations
The discussion is dedicated to document access and file sharing. NAS equipment
Also known as a file server. Receive NFS via network
Or CIFS request, the processor inside it converts these requests
Accessing only NAS you can see for SCSI block I / O commands
Storage equipment. NAS features: simple installation, high availability,
Scalability, accessibility, data can be shared, easy to manage,
Overall backup, low cost. The right picture is a schematic diagram of NAS.
2.3 SAN
Host
Host
Server
Server
Lan
San
Storage medium
Storage medium
SAN (Storage Area Network), ie store area
The internet. It separates storage devices from the network to form a
A separate network to connect all storage devices, there is a higher
Data transfer speed and better hardware performance. Storage device
In the specific network, SAN I / O requests direct access to the device, most
Number SAN uses Fiber Channel media to encapsulate in the Fiber Channel
The SCSI protocol implements the "either" host and "any" storage
The connection between the device. San implements the application at a lower level
Communication between sequence (host) and storage devices, the host will remotely
The storage medium is considered to be transmitted by long distance transmission I / O communication.
The devices visited by the road, it is accessed by blocking units, by
SAN is managed. In the above figure, the SAN schematic in the SAN schematic can use different operating systems, data coding methods, file system structures, formats, protocols, etc., and more, and the like:
Platform plan
OS / 390
Unix
Win / NT
Data encoding
Ebcdic IEEE FLOATING POINT Right Justified
ASCII
DBI. Precision f.f.f.
Right Justified
ASCII
DBI. Precision f.f.f.
Left Justified
File system structure and naming
VSAM
VTOCS-Catalogs
Aaa.bbb.ccc
JFS
Directories
DIR / XXX / YYY
FAT
Directories
DIR / XXX / YYY
format
Eckd
Clusters / Sectors
Clusters / Sectors
protocol
ESCON / OEMI
SCSI
SCSI
