RAID (Redundant Array of Independent Disks)“Redundant array of independent disks”Meaning.Disk array is composed of many cheapcapacitySmallerstabilityThe higher and slower disks are combined into a large disk group, and the performance of the entire disk system is improved by using the markup effect generated by the data provided by individual disks.At the same time, when storing data, use this technology to cut the data into many sections and store them on each hard disk.The disk array can also use the concept of Parity Check tohard disk failureCan still be readdata, onData reconstructionThe data in the failed hard disk will be reset after calculationHard diskMedium.The disk array cabinet is an external RAID equipped with many hard disks.
The principle of the disk array cabinet is to use the array mode to make disk groups, and cooperate with the design of data scattered arrangement to improve the security of data.
becausedisc driveTechnology and transmission interface technology continue to develop,disk array The design of the system faces new challenges at any time to meet the increasing requirements.A high-quality disk array cabinet must be designed in such a way that its specifications meet the requirements of disk drives with larger capacity and higher speed
Stable, high-capacity, fault-tolerant power supply system
Reliable, high-performance, fault-tolerant cooling system
Mechanical structure capable of overcoming vibration
Passive backplane supporting SCA2 hot swap connector
Integrated disk carrier without active components
Array cabinet environment monitoring and warning function
Direct hot swap and convenient maintenance and operation function
Best use of space
Meet conditions
1. The disk drive is rigidly fixed to the disk drive carrier box (no plastic or other flexible prop is used). Plastic or other flexible prop will become a vibrating amplifier, making the disk drive vibrate more severely.Fixed in a rigid way, the array cabinet designed through modal analysis can avoid the natural resonance frequency and the forced resonance frequency to minimize the system vibration and obtain the best performance, and the re seek will not be required due to the magnetic head deviation caused by the vibration.
2. The disk drive carrier box must be made of integrated rigid alloy and firmly fixed in the chassis.If the joint is made by tenon or screw, its shockproof effect can be imagined and is not ideal.[1]
Power supply system
When the disk drive motor starts, it needs a large starting current (about 2A), which is about 3 times of the normal reading and writing current (about 0.66A);When the disk drive is in SEEK, it needs a large transient current of about 2.1A, which is about three times that of about 0.66A when reading and writing.Therefore, the power supply system must be able to provide sufficient and stable instantaneous current, otherwise it will causedisc driveUnable to start, or even cause data writing errorDrivercoverraid controller It is judged as Down, but the disk drive is returned to the original factory for testing, but there is no fault.When the disk drive rotates faster and the SEEK speed increases,Power supplySufficient capacity must be provided to meet the needs of future expansion.
The dual power supply with fault tolerance, hot swapping and load sharing is indispensable. More importantly, if the power supply fails, the power supply can be hot swapped without removing screwsdisc drive〉。
YesDual power supplyThe supplier should have two sets of power inputs, one connected to the mains power supply and the other to the UPS.In this way, no matter a sudden power failure or UPS failure, RAID downtime will not occur.
A good power supply system must also have automatic selection and adjustment of AC voltage and frequency to adapt to different voltages and frequencies. More importantly, it must be able to overcome the instability of voltage and frequency.During peak period, the mains voltage may drop below 100 volts, while during non peak period, the mains voltage may rise above 120 volts, so the power supply system must be able to tolerate theseVoltage variation, provide a stable voltage and current of the disk drive, otherwise it may cause disk drive failure, or even data write errors.disk array The power supply system of the cabinet should be able to provide stepless automatic adjustment from 85 to 260 volts. In this way, no matter what kind of socket is plugged in, the function of the disk array will not be affected by how the quality of the mains power changes.
Cooling system
In many cases, we found that the cooling system design is not perfectdisk array Cabinet, only 7200 rpmdisc driveIf a 10000 rpm disk drive is used, the system will overheat.Seagate has launched 15000 rpm disk drives. How to select a disk array cabinet with a reliable, high-performance, fault-tolerant cooling system is even more important.
In the design of general disk array cabinets, small fans are added to each disk drive carrier, and several large fans are added to the whole system to cool the system by suction and blowing. Not only is the cooling effect not good, but also it is a potential factor for disk drive failure: the hazards it brings are as follows:
A large amount of airflow is generated to blow dust into the system, polluting the disk drive and the fan itself, causing failure.
Small fans for general PC are used, and the number is large (the more rotating mechanical parts are, the higher the failure probability is),System reliabilityAs a result, it is greatly reduced.
Once a small fan fails, relevantdisc driveIt will fail because it cannot get enough heat dissipation.
A high qualitydisk array The design of the cooling system of the cabinet must fully comply with the thermodynamic theory of all-round cooling: the three-phase heat dissipation mode of heat conduction, heat convection and heat radiation, in order to be more efficient and reliable:
The disk drive carrier box must be made of black, high thermal conductivity metal (such as aluminum alloy), and be in close contact with the carrier box, so that the heat energy of the disk drive can be transmitted to the whole carrier box as quickly and effectively as possible, and then the heat energy can be radiated to the air in the body with the maximum radiation area and the best radiation color (black),Then the hot air is discharged by convection through the central system turbine exhaust fan
disc driveFan and any other active components cannot be used in the carrier box to avoid damage to the disk drive due to its own failure
The system adopts the central exhaust and heat exhaust design, and must use more than two industrial turbine exhaust fans (ordinary PC fans are not available) to improve reliability and heat exhaust efficiency.For industrial useTurbine exhaust fanIt can prevent the bearing from being polluted by dust, and the air extraction efficiency is extremely high. It can draw out the hot air in the machine body and generate a large relative low pressure in the machine body, so that the cold air can enter the machine body evenly from the precisely designed convection hole to achieve the best convection heat dissipation effect.
The central system turbine exhaust fan must have the function of heat extraction and exchange, and be able to automatically control the temperature and speed to achieve the best heat removal performance and energy efficiency. Only one turbine exhaust fan is enough to maintain the minimum heat dissipation of the system.The outlet area of industrial turbine exhaust fan is only 1/10 of that of general PC fan, so even if any fan stops for some reason, the thermal convection structure of the whole system will not be affected.
Shockproof mechanical structure
becausedisk array When accessing the data in the arraydisc driveAt the same time, the magnetic heads of the two brakes brake in the same direction and at the same position at the same time, and their inertia momentum is very large.Therefore, it causes great vibration problems.If the mechanical structure of the disk array cabinet cannot overcome these vibration problems, it may cause Re Seek, or serious damage to the disk surface and data loss.
A good mechanical structure design of the disk array cabinet must overcome the above vibration problems:
The disk drive is rigidly fixed to the disk drive carrier box (no plastic or other flexible prop is used): plastic or other flexible prop will become a vibrating amplifier, making the disk drive vibrate more severely.Fixed in a rigid manner, the array cabinet designed through modal analysis can avoid the natural resonance frequency and forced resonance frequency, minimize the system vibration, obtain the best performance, and do not need to re seek the track due to the magnetic head offset caused by vibration.
The disk drive carrier box must be made of rigid alloy and tightly and firmly fixed in the chassis.If the joint is made by tenon or screw, its shockproof effect can be imagined and is not ideal.
Passive backplane
As mentioned earlier,disk array The most important thing of the system is reliability, so all active components (including electronic components and mechanical components) must be installed on hot swappable modules, so that they can be replaced at any time in case of failure.In general, passive components cannot be broken unless violence is directed against them.
In the disk array cabinet, except for the backplanemodularThey can be hot swappable.Therefore, the backplane cannot have any active components, so as to avoid any component failure and the need to stop the machine for replacement. In general, users cannot replace the backplane by themselves.
Another important specification of the disk array cabinet backplane is that SCA2 connectors must be used to support hot swapping.We all know thatdisc drivePulling out or inserting from the system will cause a large burst signal, which may affect the working Bus, or even damage the disk drive interface components. Therefore, special design must be made to reduce and prevent the damage caused by the burst.
The design of SCA2 connector is to use long, medium, short and other different length pins to connect the power supply and ground wire, main power supply, bus signal wire, etc. in the early stage in order to contact (insert) or separate (pull out), so that the disk drive circuit can be slowly charged, and its potential can be raised to reduce the potential difference between it and the bus, so as to reduce the spike signal,Protect the electronic interface components and avoid interference with the bus in operation.
Disk carrier
In actual cases, it is often found that users send the disk cartridge for repair because the disk cartridge buzzer keeps ringing and the fan is stuck.of course,disc driveIt may also be overheated and destroyed.This is caused by the poor design of the disk carrier.
A good disk carrier design must not use any movable mechanical or active electronic components, that is, no small fan or any control circuit.In this way, the disk carrier itself is an indestructible body, which will not cause failures, and will not become a disk drive killer.
At the same time, the fixed mode of disk drive is also a subject.In addition to the above, the disk drive should be directly and tightly fixed on the disk carrier box to achieve heat conduction and cooling, and the disk drive should preferably be fixed upside down.If general front fixing is adopteddisc driveThe generated heat is transmitted to the disk carrier box, and then radiates out to generate hot air, and then rises. The circuit boards and components just used to bake the disk drive will accelerate the aging of the components.If upside down fixing is adopted, the heat transmitted to the disk carrier box will radiate to the upper space of the disk drive, which will be taken away by the convection airflow, and will not bake to the disk drive circuit components.
In order to achieve the best thermal radiation and heat dissipation effect, the surface of the disk drive carrier box should be painted black, because black is the color that is easiest to absorb heat energy, and is also the color that is easiest to radiate heat energy.The material of the disk drive carrier box must have the characteristics of high thermal conductivity. For example, aluminum alloy can identify the ideal material with high thermal conductivity and easy processing.
As mentioned above, the disk drive carrier box must be made of rigid metal alloy in an integrated manner to achieve the best vibration overcoming performance.We strongly do not recommend the use of combined disk carriers. Generally, these combined disk carriers are composed of a shelf and a box;There are fans and hot swap control circuits on the shelf, which are fixed on the chassis and connected to the cable;disc driveIt is installed in a box and connected to the shelf through the adapter.In this way, not only the vibration problem mentioned above is caused, but also the fan or electronic components of the rack must be stopped for replacement once they fail.
Monitoring and warning function
disk array All active components or mechanical components in the cabinet, as well as the internal ambient temperature, must be able to monitor and have appropriate warning and notification functions:
Array controllerMust be able to support SM.A.R.T.，So as to predict the possibledisc driveFault.Make good use of SM. The A.R.T. function can prepare the spare disk drive in advance to replace the unstable disk drive at the first time, so as to minimize the risk factor.
Environmental statusmonitorMust be able to monitor at any timecabinetInternal temperature, and control the speed of the drainage device to achieve optimal cooling andEnergy efficiency。
The input and output of the power supply must also be monitored at any time.At the same time, abnormal conditions must be reported in two or more ways, at least includingarraySound and visual light warning of the cabinet itself, as well as remote notification.
In addition, it is very important that the environment monitoring controller itself is an active component, which may also fail. Therefore,disk array The environmental monitor of the cabinet must be able to support the hot swap function.
Maintenance and operation functions
staydisk array In the cabinet, all components that may fail, including active electronic components and movable mechanical components, must be able to support the hot swap function.Components that cannot be replaced must be passive components that will not fail.
It is well known that it has the function of heat exchange, but how to make heat exchange more convenient and safe is a subject.A disk array cabinet providing convenient maintenance and safe hot swapping shall at least have the following functions:
All components that can be hot swapped must be able to be directly swapped from the outside without removing other components first, so as not to cause any risk.Imagine that if a fan breaks down, you need to remove a power supply before you can replace the broken fan. You must ensure that the remaining power supply will not fail, otherwise······
For all hot pumping and changing operations, it is not necessary to put hands or tools into the body to disassemble screws or pull out joints.If the tool is inserted into the machine body, it may touch the circuit by mistake, causing a short circuit, and the whole system may be damaged or crashed;If you put your hand into the machine body, you may get an electric shock. Once a person gets an electric shock, the reaction is unpredictable and uncontrollable, which may damage the whole bodydisk array The cabinet swung five meters away.
No tools are required for all hot pumping and changing operations.It is very dangerous to use tools on the system in operation. Turning the screws forcefully will cause the body to shake,disc driveWill be damaged;Metal tools can also cause short circuits.
All components that can be hot swapped cannot be fixed with screws, because if you are not careful, the screws may fall into the body, causing a short circuit.If you must use screws, you should also use screws with tenons. After being removed, they can still be safely stuck on the components without falling off.
Space utilization
In a rack mounted system, the utilization of space and the demand for cooling airflow are very important factors.It can also accommodate seven setsdisc drive, one only occupies 3U spacedisk array Cabinet, of course, is more efficient than a disk array cabinet that occupies 6U of space.
In order to achieve optimal space utilization, in addition to the small size of the disk array cabinet, the demand for cooling airflow is also a decisive factor.A disk array cabinet that is only used for unidirectional convection cooling requires a large air flow demand to achieve the cooling effect. Therefore, even if the size is small, you cannot install too many disk array cabinets in a rack, or the cooling air flow will be insufficient.
If the disk array cabinet adopts an efficient three-phase heat dissipation (heat conduction, heat radiation, heat convection) system, only a small amount of air flow is required to give full play to the heat dissipation effect. Therefore, the disk array cabinet can be installed in the rack with high density, greatly improving the space use efficiency, and of course, greatly reducing the cost.This is important for large enterprises, ISPshostFor the agent, it is a very cost-effective specification.
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becausedisk array Cabinet hasdata storage Because of its advantages such as high speed and large storage capacity, the disk array cabinet is usually suitable for small and medium-sized central cluster networks inside enterprisesStorage areaMass data storage.
