Open system direct attached storage (DAS for short) has been used for nearly 40 years. With the continuous growth of user data, especially when it is over hundreds of gigabytes, its problems in backup, recovery, expansion, disaster recovery and other aspects become increasingly troublesome to the systemadministrators。
The connection channel between the direct attached storage and the server host usually uses SCSI connection. As the processing capacity of the server CPU becomes stronger and stronger, the storage hard disk space becomes larger and larger, and the number of hard disks in the array becomes more and more, the SCSI channel will become the IO bottleneck;The SCSI ID resources of the server host are limited, and the SCSI channel connections that can be established are limited.
Chinese name
DAS direct attached storage for open systems
Foreign name
(Direct-Attached Storage
Overview
In terms of backup, recovery, expansion, disaster recovery, etc
Assembly instruction
Instruction action correction process
data management
System Introduction System Features Basic Functions
Correction AL consists of two combinationsBCD codeThe result of direct subtraction is stored in AL
Calibration process
If (AL&0FH)>9 or the auxiliary carry flag A=1 (that is, the single digit is not enough to be subtracted, and borrowing is required), then: the value of AL is subtracted by 6 (the lower 4 digits are corrected)
„ Auxiliary carry flag A is set to 1;If AL>9FH or the carry flag C=1 (that is, ten digits are not enough to be subtracted, and borrowing is required), then:
„ The value of AL is reduced by 60H (the upper 4 digits are corrected), and the carry flag C is set to 1
Influence on flag register
Affects flag bits S, Z, A, P and C, but does not define overflow flag bit O
Application examples
(AL)=12H (combined BCD code of 12), (BL)=34H (combined BCD code of 34), calculate the value of 12-34.Directly execute the subtraction instruction:
After SUB AL, BL, (AL)=0DEH, obviously the result is incorrect, and needs to be corrected: DAS
DASThe command automatically completes the following operations: because the low 4 bits of AL carry to the high 4 bits during subtraction, AF=1, so:
„ (AL) ← (AL) - 6, that is, (AL)=0DEH - 6=0D8H
AF=1
Since AL>9FH when adding
„ (AL) ← (AL) - 60, that is, (AL)=0D8H - 60=78H
„ CF=1
Finally, CF=1, (AL)=78H (because 112 - 34=78)[1]
Direct attached storage
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Direct attached storage depends on serversHost operating systemPerform IO read/write and storage maintenance management of data,Data backupAnd recovery require server host resources (including CPU, system IO, etc.), and data streams need to be returned to the host and connected to the serverTape drive(Library), data backup usually occupies 20-30% of server host resources, so many enterprise users' daily data backup is often carried out late at night or when the business system is not busy, so as not to affect the normal operation of the business system.The larger the amount of data stored directly, the longer the backup and recovery time, and the greater the dependence and impact on server hardware.
The connection between direct attached storage and server host usually adoptsSCSIThe bandwidth is 10MB/s, 20MB/s, 40MB/s, 80MB/s, etcCPUThe processing capacity of the SCSI channel will become the IO bottleneck with the increasing capacity of the storage hard disk and the number of hard disks in the array;The SCSI ID resources of the server host are limited, and the SCSI channel connections that can be established are limited.
No matter the expansion of direct attached storage or server host, from one server to a cluster composed of multiple servers, orStorage arrayThe expansion of capacity will cause downtime of business systems, which will bring economic losses to enterprises. This is unacceptable for key business systems with 7 × 24 service in banking, telecommunications, media and other industries.In addition, the upgrade and expansion of direct attached storage or server host can only be provided by the original equipment manufacturer, which is often limited by the original equipment manufacturer.
DAS model
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The DAS (database as a service) model is a new onedata managementModel, which stores user data in
The model puts forward higher requirements for the security of outsourced databases: it can not only prevent external attackers from stealing or tampering with important data, but also
It can also prevent illegal access of DSP internal personnel.
The internal personnel of the enterprise intend to passE-mail, chat tools and other important information are leaked, which benefits competitors and makes enterprises fail repeatedly in business competition.
Spreading rumors through the Internet, insulting and slandering others
Because of the openness of the Internet, anyone has the opportunity to participate in online forums, blogsBBSAnd other places to make comments to provide opportunities for people with ulterior motives.These people fabricate facts and slander others on the Internet, causing adverse effects. They know that it is the work of internal personnel of the enterprise, but they cannot accurately locate it.Sudden change of network traffic, unable to find the cause
Companynetwork data Congestion occurs, and it is impossible to determine who is occupyingnetwork resource, nor can we know which websites employees are browsing.
Chaotic network applications
Emergence of enterprisesOA, financial management and other key businesses are blocked, and the enterprise office network is suddenly paralyzed;No statistical analysis was made on the records of online identities and behaviors such as IP, visiting sites, chat tools, forum speeches, etc;The functions of enterprise system software and hardware have not been brought into play.
Function model
Product model
Provide a variety of equipment models from medium to group
Hardware specifications
1U~4U shelf mounted equipment, see the actual hardware model description for specific specifications
Network access
Support static IP, PPPoE client, DHCP client access network
Network mode
Support data analysis under VLAN, PPPoE, Layer 3 switching, DHCP and other networks
Behavior record
Support the recording of online behaviors such as web pages, emails, forums, blogs, searches, chats, games, securities, etc
Content Restore
Support content restoration of network behaviors such as forum, blog, email, chat, search, etc
Real time monitoring
Support real-time monitoring of all online behaviors
data statistics
Support the statistics and analysis of the depth, frequency, track, association, etc. of all behaviors and contents
Analysis report
Support report generation and typesetting printing of all records and statistics
Hierarchical deployment
Support distributed deployment and centralized management
Image monitoring
Support HUB, stream image, port image, two-layer image, three-layer image and other data source analysis
Policy alarm
Support user-defined policy alarm for all online behaviors
association analysis
Support the correlation analysis of the track, behavior, history, etc. of the virtual identity
system maintenance
Provide system management based on WEB and command line, and support remote upgrade
Solution
By deploying "DASnetwork analysisThe system can effectively track the records of virtual identities and network behaviors, restore the use of the network, and combine the relationship between real people and virtual identities to provide objective and effective data such as network behaviors and network traffic for decision-making, and ultimately ensure the smooth progress of core business.
“DASnetwork analysisThe system has comprehensive network analysis functions, providing records of various network behaviors such as web browsing, email sending and receiving, chat, games, search, and related virtual identities, as well as various practical functions such as advanced behavior analysis, monitoring alarm, flow analysis, statistical report, and trajectory analysis, to comprehensively analyze the network operation from multiple perspectives.The product supports distributed deployment and bypass access that has no impact on existing network conditions.
DAS means direct connectionstorage, the full English name is Direct Attached Storage.
The Chinese translation is "direct attachment"storage”。As the name implies, in this way,
The storage device is via cable (usuallySCSI interfaceCable) directly to the server.I
IO (input/output) requests are sent directly to the storage device.
DAS，It can also be called SAS (Server Attached Storage).It depends on the server. It is a stack of hardware without any storageoperating system。
Advantages and disadvantages
advantage:
1. It can realize mass storage and combine multiple disks into one logical disk to meet the requirements of mass storage
2. It can realize the separation of application data and operating system: the operating system is generally stored in the local hard disk, while the application data is placed in the array
3. It can improve the access performance: it can operate a single file, while multiple physical disks are working in parallel, and the running speed is higher than that of a single disk
4. Simple implementation: no professional operation and maintenance is required to save user investment.
Limitations:
1. The server itself is easy to become a systembottleneck
2. The server fails and the data is inaccessible
3. For a system with multiple servers, the equipment is scattered and difficult to manage.When multiple servers use DAS at the same time, storage space cannot be allocated dynamically between servers, which may cause considerable waste of resources;
1) The servers are geographically distributed, and they are distributed through SAN（Storage Area Network）Or NAS (network direct storage) is very difficult to interconnect between them (branches of stores or banks are a typical example);
2）storage system Must be connected directly toapplication server (such as the "original partition" used by Microsoft Cluster Server or some databases);
3) Including many database applications andapplication server Applications that need to be directly connected tostorageGroupware applications and some mail services are also included.
Typical DAS structure is shown in the figure
For an environment with multiple servers or PCs, the initial cost of using DAS may be low. However, under this connection mode, each PC or server has its own storage disk, which makes capacity reallocation difficult;For the whole environmentstorage system Management is tedious and repetitive, and there is no centralized management solution.So the overall cost of ownership（TCO）Higher.At present, DAS is basically replaced by NAS.The following is the DAS andNASComparison of.
DAS: It can also be Data Access Sessions in SOA architectureIt is used to create the Data Graph, and the key (SDO) in SOA depends on the existence of the Data Graph
data management
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DAS electronic clinical data management system (DAS for eCDM for short) is composed ofShanghai University of Traditional Chinese MedicineThe electronic clinical data collection and management (EDC/eCDM) system jointly developed by the Pharmaceutical Clinical Research Center, Shanghai Bojia Pharmaceutical Technology Co., Ltd. and other units, with reference to foreign peer standards, can conduct remote data collection and management for Phase I to IV clinical trials.Based on the Internet platform, the system establishes electronic case report forms (eCRF), and researchers in each center can transmit research data online to the DASforeCDM systemData Center；The supervisor shall conduct online monitoring at any time, issue questions about the data in question in a timely manner, and the researcher shall respond to the questions online synchronously;dataadministrators(DM) Lock the data reviewed by the supervisor, and finally export the data for statistical analysis.
System Introduction
DAS for eCDM system is composed ofShanghai University of Traditional Chinese MedicineThe electronic clinical data collection and management (EDC/eCDM) system jointly developed by the Drug Clinical Research Center, Beijing Bozhiyin Technology Co., Ltd. and other units can conduct remote data collection and management for Phase I to IV clinical trials.Based on the Internet platform, the system establishes electronic case report forms (eCRF), and researchers in each center can transmit research data online to the DAS for eCDM systemData Center；The supervisor shall conduct online monitoring at any time, issue questions about the data in question in a timely manner, and the researcher shall respond to the questions online synchronously;The data manager (DM) locks the data reviewed by the supervisor, and finally exports the data for statistical analysis.
System characteristics
Visual eCRF editing function, easierdata collection, synchronous automatic verification of data doubts, reducing errors and improvingData quality, different users and roles selectively have access to data to ensuredata security, keep all user data operation traces for future reference.The system is compatible with different laboratory inspection results of different research institutions, and synchronous online monitoring ensures the timeliness and correctness of data.Multi level structure of data submission, data review and data locking, and synchronous audit by the third party.Subjects' enrollment, audit traces, questions, etcreport formReal time automatic generation, data result printing and transmission, data export.
DAS for eCDM Advantage Security Assurance
◆ Ensure that the data can be timely, complete and accurate ◆ Only authorized personnel can enter the system
Ensure legal access to the database
◆ Timely discover data errors ◆ selectively have access to data
◆ Reduce research costs ◆ Automatically retain all operation traces
◆ Keep data operation trace for future reference ◆ Print and transmit data results
◆ Compatible with different research institutions ◆ Data export
Laboratory inspection results
driving system
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The diversity drive system DAS can reduce the probability of serious accidents caused by specific transient and common mode faults that are rarely likely to occur in the protection and control system.
AP1000 Protection and Safety Monitoring System（PMS）The Common Q system adopted by the system has passed the common mode fault test including extreme temperature and humidity environment, earthquake, electromagnetic compatibility and software common mode fault.The tests on earthquake, environment and electromagnetic compatibility prove that these conditions will not affect Common Qhardware system A common mode fault has occurred.software systemA variety of methods are also used to minimize the possibility of common mode failure. In addition, the software design process includes the review of unexpected events to determine which safety functions may be affected by software common mode failure.
These safety functions that may be affected by common mode faults of software must be completed by diversified methods.These safety functions that may be affected are combined to form a diversified drive system (DAS), which is used to mitigate the impact of software common mode failure of normal safety systems.
DAS is a diversified backup system for software common mode faults that are unlikely to occur in PMS system. In case of hypothetical common mode faults in PMS system, the risk will be reduced.Since the PMS system itself is earthquake resistant, the DAS system does not consider the common mode failure caused by the earthquake. Since the PMS is passive cooling, the common mode failure caused by the loss of ventilation is also not considered.Therefore, DAS only meets the requirements of Seismic Category II, and it is not required to be Class 1E, nor to operate without ventilation.
DAS system is an isolated system, independent of other power plant control and monitoring systems, and its operation does not depend on the power plant data network (DCS network).
DAS has the following three main functions:
Automatic drive function, that is, when the parameters of the power plant exceed the set value, provide diversified and redundant automatic drive signals to shut down the reactor or drive the selected engineered safety facilities.
Manual actuation function, which provides independentHardwired, manual drive function.
Display and alarm functions provide special and independent display for selected power plant parameters.
Distributed antenna system
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The problem faced by wireless devices is that in a facility or campus, each wireless application usually needs its own wired infrastructure access point and other wireless transmission sources.The result is a separate, redundant infrastructure.This infrastructure creates a chaotic RF environment and hampers wireless applications.A shared broadband indoor passive distributed antenna system (DAS) brings new order to such a chaotic environment, thus making high-quality wireless services possible.This antenna system can support various wireless technologies provided by different manufacturers in a wide frequency range.
The core of passive antenna is an integrated access device (IAD).The cellular/PCS, two-way radio and paging systems are connected to the IAD through the base station or the off air repeater.Various services are combined and filtered, and then transmitted using wired backbone lines or trunk lines (typically 7/8-inch coaxial cables) connecting all floors of the building.
A well-designed antenna array is led out from the trunk line on each floor to transmit RF energy.The antenna array includes radiation coaxial cable, standard coaxial cable, directional antenna and omnidirectional antenna.The antenna array is configured on a per floor basis to provide coverage in a specific area and maintain RF signals within the facility.
Since applications such as WLAN, building automation and security systems usually serve a local area, they are added to passive DAS floor by floor.Local applications connect through application portal devices like IAD.The application portal device integrates RF energy from multiple sources and adds these signals to the antenna array.This method requires detailed site investigation and in-depth understanding of building structures and materials.
A passive DAS can handle multiple frequencies for integrating voice and data, building automation and security services.Base stations and/or wired repeaters from multiple service providers are centrally placed in a main telecommunications room.Access points are centrally located in the locked middle distribution facility area on each floor.
A stack zone can provide coverage for a site with an area of 500000 square feet.As required, fiber optic repeaters provide signals for more areas requiring larger facilities for one IAD.
In fact, a passive DAS is a huge, highly efficient antenna that distributes RF energy evenly to all corners of the building.DAS does not require amplifiers or repeaters.All components of the system are passive: they are non mechanical and do not require power supply.Therefore, the system does not need monitoring and has high reliability.It is a utility system just like the power distribution and HVAC (heating, ventilation and air conditioning) distribution system.
DAS follows IEEE 802.11 standard.They also support CDMA, GSM, IDEN (Integrated Digital Enhanced Network), TDMA, GPRS and UMTS standards.They can support a continuous broadband frequency range from 400MHz to 2.5GHz.This frequency range covers most indoor wireless applications and emerging technologies.
At the same time, a single infrastructure supporting multiple applications will reduce interference and provide reliable wireless coverage in a building.
