Over the past ten years, in the same organizational structure in the setting of multiple servers to complete the different multi-task much faster way of expertise.Server as a wide range of application processing, such as a database application, web services, transaction processing and application settings, and more.Although the organizational structure to rely on the server to complete the task of classic service, based on INTEL processor-based servers accounted for the main position, disk storage is widely used to store the file or processing a print issues.
File server is not only widely used, and matters involving a wide area: from large enterprises to departments, shopping malls, sub-offices and small companies.Transactions required to achieve safe storage and file saving too.
Servers need to connect the hard disk storage technology in general is a direct memory connection (Direct Attached Storage DAS).This approach is assigned to each corresponding to a server hard disk storage.Although the setting and the purchase of the implementation of DAS is very simple and direct, we soon realized that each new store investment can only correspond to a specific server.For the effective utilization of DAS storage and management of the main challenges soon become an administrator.
Easily set in the DAS server at the same time also implies some disadvantages.Some of the server's disk storage utilization up to 90%, while some only 30% or 40%.If the utilization rate multiplied by 10 or 100, for some large enterprises, their IT department store on the server is not effectively utilized.Further utilization of the issues we will find the cause of this problem is the connection DAS can not be shared between the server storage resources.Another problem is the DAS server programs do not have a central storage management, such as data backup and recovery, the need for each server independently.
Server's hard disk storage capacity, low utilization problem, some servers run out of storage space, need not be a single management a certain amount of shared storage resources, lack of flexibility, all of these weaknesses result in waste of resources, potentially leading to higher managementpressure and high costs.These deficiencies need to promote the storage industry to develop a new disk storage technology to solve these problems.
Programs using a shared storage pool
In order to solve the problem DAS weakness, a new hard disk storage solutions emerged, the integration of a single shared storage pool.This program can give users two main benefits: lower costs and simplify management.The purpose of the storage pool is stored in the physical isolation of the island will be integrated into large areas of land, thereby to increase storage utilization.Are thus to reduce the different management tools to effectively achieve a variety of tasks such as data backup.All of these benefits will effectively reduce the customer's total cost.
Highlight the existing hard disk storage consolidation in two ways: Networked Attached Storage (NAS) and Storage Area Networks (SANs).Although these two methods are shared to achieve the purpose of storage, but they each have their own strengths and weaknesses --- depending on the application and the existing IT environment.
Storage Area Network Storage Area Networks (SANs)
SAN is a dedicated hard drive storage devices and servers by a network of servers and storage devices has changed the traditional way of correspondence.SAN environment with a shared storage pool.
SAN connections and Local Area Networks (LANs) of the design theory is the same as Lu also has a device, adapters, switches and gateways, but SAN is commonly used but more expensive, high-performance technology - fiber as itsmedia media.
SAN using the I / O protocol for fiber-optic protocols Fibre Channel Protocol (FCP), called Serial SCSI command protocol.Store data I / O mode is "block I / O", because the only direct connection to the hard disk, the read and write I / O command is directly targeted at a specific device and a particular sector on the hard disk to carry out the.
SAN is an excellent solution for high performance, especially for databases, mail and transaction processing applications.SAN performance can be improved to provide high rate, the software allows multiple SAN devices to a single storage pool before the server appears in the SAN.SAN can achieve a single point of management, without a variety of management tools.
Network Attached Storage Network Attached Storage (NAS)
Consists of three parts: the server, storage (internal / external), the operating system.
NAS is hard disk storage device optimization, so through the existing TCP / IP network to meet the concept of file sharing.NAS solutions are easy to implement and cost is not high, because most of the customers have been setting up the LAN environment.
Familiar with through existing structures to implement the NAS IP pool will give us benefits.SAN environment, the cost to build the general was at the end, because it needs the basic LAN environment and major equipment already in place.SAN environment than in terms of cost structures are much lower.NAS can use existing technology and supported by IT resources to achieve, which can greatly reduce customer costs.
How to distinguish between these three ways
Terms from the physical connection, DAS is a one to one server and disk storage, SAN and NAS is shared storage pool.
However, in terms of difference from the physical connection is not so obvious limits, NAS server environment can be directly attached storage cabinet as EXP400/DS300/400, FastT and so on, similar to the DAS, DS300 is taking the TCP / IP protocol,Why is it not a NAS but the SAN storage?
Here we look at their store data to distinguish between two different I / O mode - FILE I / O and BLOCK I / O.
FILE I / O - the operating system will format your hard drive, create a partition on the hard disk file system structure.Operating system through the file system to achieve the positioning data on the hard disk.
BLOCK I/O-- operating system does not format your hard drive, did not produce the file system partition on the hard disk.Is the application (SQL) to bypass the OS to directly target read RAW DISK (sectors) of data.
NAS is a data read mode FILE I / O, when users exchange data with the NAS server, when requested by the operating system to achieve, for the positioning of hard drive data sector through the NAS's operating system later be used to achieve.
Such as the customer wants to access a 1M file, can not access this file 10KB only part of the entire file must be opened, so I FILE I / O.DAS and SAN through the BLOCK I / O (RAW I / O) to directly target the hard drive data, high efficiency, which is why the high-performance SAN one of the reasons.
NAS Gateway
NAS gateway role is to FILE I / O into BLOCK I / O (NAS and SAN will combine the advantages)
Allows different operating systems in different application clients can access data stored on the server hard drive, fast access to stored data to play SAN features.