阅读说明：本技术 数据储存系统的控制方法、数据储存模块、电脑程序产品 (Control method of data storage system, data storage module and computer program product ) 是由 谢正光 陈楷升 蔡家铭 陈义皓 于 2018-09-17 设计创作，主要内容包括：本发明提供了一种数据储存系统的控制方法、数据储存模块、电脑程序产品,所述数据储存系统的控制方法,包括藉由一控制装置取得多个储存装置的相关系数；以及藉由所述控制装置调整所述多个储存装置的一个存储装置的连接速度。本发明可以调整部分储存装置的连接速度,进而增进数据储存系统的整体效能。(The invention provides a control method of a data storage system, a data storage module and a computer program product, wherein the control method of the data storage system comprises the steps of obtaining correlation coefficients of a plurality of storage devices by a control device; and adjusting, by the control device, a connection speed of a storage device of the plurality of storage devices. The invention can adjust the connection speed of part of the storage devices, thereby improving the overall efficiency of the data storage system.)

1. A method of controlling a data storage system, comprising:

obtaining correlation coefficients of a plurality of storage devices by a control device; and

adjusting, by the control device, a connection speed of a storage device of the plurality of storage devices.

2. The method of claim 1, wherein the plurality of storage devices are rotating hard disks.

3. The method as claimed in claim 1, wherein the correlation coefficient is based on a performance comparison value and a location parameter of each of the plurality of storage devices, the location parameter corresponding to a distance between each of the plurality of storage devices and a fan, and wherein the control device decreases the connection speed according to the correlation coefficient.

4. The method of claim 3, further comprising:

setting the location parameter for each of the storage devices via the control device; and

and obtaining the performance comparison value of each storage device through the control device.

5. The method of claim 1, wherein the connection speed is adjusted down when the correlation coefficient is greater than a predetermined correlation value.

6. The method of claim 1, further comprising throttling down a fan speed via the control device based on the correlation coefficient.

7. The method of claim 1, further comprising:

obtaining a threshold temperature value of each storage device through the control device; and

and when the operating temperature of one of the storage devices exceeds a threshold temperature value of the one of the storage devices, increasing the rotation speed of a fan through the control device.

8. The method of claim 3, further comprising:

obtaining a reference performance value of each storage device;

obtaining an actual performance value of each storage device; and

and obtaining the performance comparison value of the storage device through the control device according to the actual performance value and the reference performance value.

9. The method as claimed in claim 8, wherein the performance comparison value for one of the plurality of storage devices is derived from a difference between a reference performance value and an actual performance value for the one of the plurality of storage devices.

10. The method as claimed in claim 8, wherein the distance between the fan and one of the storage devices with the connection speed reduced is less than the distance between the fan and the rest of the storage devices.

11. The method as claimed in claim 8, wherein the performance comparison value of one of the plurality of storage devices with the connection speed reduced is greater than the performance comparison values of the remaining storage devices.

12. A data storage module, comprising:

a plurality of storage devices;

a plurality of fans adjacent to the plurality of storage devices; and

a control device electrically connected to the plurality of storage devices and the plurality of fans;

wherein one of the storage device and the fan is arranged in sequence along an arrangement direction;

wherein the apparatus adjusts a connection speed of one of the plurality of storage devices or a rotation speed of one of the plurality of storage device fans according to a correlation coefficient of the plurality of storage devices.

13. The data storage module of claim 12, further comprising a housing removably disposed within a rack, wherein the plurality of storage devices and the plurality of fans are disposed within the housing.

14. The data storage module of claim 12 wherein each of the storage devices corresponds to a performance comparison and a location parameter, and the location parameter corresponds to a distance between each of the storage devices and one of the plurality of fans, wherein the performance comparison and the location parameter correspond to the correlation coefficient.

15. A computer program product loaded via a processor to perform the method of claim 1.

Technical Field

The invention mainly relates to a control method of a data storage system, a data storage module and a computer program product.

Background

Existing data storage centers have multiple data storage devices to store large amounts of digital data. Each data storage device has a large number of hard disks, and generally the number of hard disks in a data storage device can exceed one hundred. However, when a large number of hard disks operate at high speed, a large amount of heat energy is generated, and therefore, a plurality of fans are disposed in the data storage device to dissipate heat from the hard disks.

However, when the rotation speed of the fan is increased, a resonance phenomenon may occur, which may cause the performance of a portion of the hard disk to be greatly reduced, thereby affecting the performance of the data storage device.

Disclosure of Invention

The invention provides a control method of a data storage system, a data storage module and a computer program product. The data storage module can reduce the influence of the resonance of the fan on the efficiency of the data storage module according to the operating conditions of the fan and the storage device.

The invention provides a control method of a data storage system, which comprises the steps of obtaining correlation coefficients of a plurality of storage devices by a control device; and adjusting, by the control device, a connection speed of a storage device of the plurality of storage devices.

In some embodiments, the correlation coefficient is based on a performance comparison value and a position parameter of each of the plurality of storage devices, and the position parameter corresponds to a distance between each of the plurality of storage devices and a fan, wherein the control device decreases the connection speed according to the correlation coefficient.

In some embodiments, the method further comprises setting the location parameter for each of the storage devices via the control device; and obtaining the performance comparison value of each storage device through the control device.

In some embodiments, the connection speed is adjusted down when the correlation coefficient is greater than a predetermined correlation value.

In some embodiments, the control device adjusts the rotation speed of a fan according to the correlation coefficient. In some embodiments, the storage device is a rotating hard disk.

In some embodiments, the method further includes obtaining a threshold temperature value of each of the storage devices by the control device; and increasing the rotation speed of a fan through the control device when the operation temperature of one storage device in the plurality of storage devices exceeds the critical temperature value of one storage device in the plurality of storage devices.

In some embodiments, the method further includes obtaining a baseline performance value for each of the storage devices; obtaining an actual performance value of each storage device; and obtaining the performance comparison value of the storage device through the control device according to the actual performance value and the reference performance value.

In some embodiments, the performance comparison value of one of the plurality of storage devices is obtained according to a difference between a reference performance value and an actual performance value of the one of the plurality of storage devices.

In some embodiments, the distance between one of the storage devices, the connection speed of which is reduced, and the fan is smaller than the distance between the remaining storage devices of the plurality of storage devices and the fan. In some embodiments, the performance comparison value of one of the plurality of storage devices, the connection speed of which is reduced, is greater than the performance comparison values of the remaining storage devices of the plurality of storage devices.

The invention provides a data storage module, which comprises a plurality of storage devices, a plurality of fans and a control device. The plurality of fans are disposed adjacent to the plurality of storage devices. The control device is electrically connected with the storage device and the fan. The storage device and the fan are sequentially arranged along an arrangement direction. The control device adjusts the connection speed of one of the storage devices or the rotation speed of one of the fans according to a correlation coefficient of the storage devices.

In some embodiments, the data storage module further includes a housing detachably disposed in a rack. The plurality of storage devices and the plurality of fans are arranged in the shell.

In some embodiments, each of the storage devices corresponds to a performance comparison value and a location parameter, and the location parameter corresponds to a distance between each of the storage devices and one of the plurality of fans, wherein the performance comparison value and the location parameter correspond to the correlation coefficient.

The invention provides a computer program product, wherein the computer program product is loaded by a processor to execute the control method of the data storage system.

In summary, the control device of the present invention can detect whether the operation performance degradation of the storage device is caused by the resonance of the fan. If the operating performance of the storage device is reduced due to the resonance of the fan, the connection speed of a part of the storage device can be selectively adjusted, or the rotating speed of the fan can be further adjusted, so that the overall performance of the data storage system is improved.

Drawings

FIG. 1 is a schematic diagram of a data storage system according to some embodiments of the present invention.

FIG. 2 is a perspective view of a data storage device according to some embodiments of the present invention.

FIG. 3 is a schematic diagram of a data storage module according to some embodiments of the present invention.

FIG. 4 is a flow chart of a method of controlling a data storage system according to some embodiments of the present invention.

FIG. 5 is a flow chart of a method of controlling a data storage system according to some embodiments of the present invention.

FIG. 6 is a flow chart of a method of controlling a data storage system according to some embodiments of the present invention.

Reference numerals:

data storage system A1

Data storage device 1

Control device 2

Rack 10

Data storage module 20

Case 21

Rear side 211

Storage device 22

Fans 23, 23a, 23b, 23c, 23d

Controller 24

Alignment directions D1 and D2

First row R1

Second row R2

Third row R3

Fourth row R4

Fifth row R5

Sixth row R6

Detailed Description

The following description provides many different embodiments, or examples, for implementing different features of the invention. The particular examples set forth below are illustrative only and are not intended to be limiting.

FIG. 1 is a schematic diagram of a data storage system A1 according to some embodiments of the present invention. Fig. 2 is a perspective view of a data storage device 1 according to some embodiments of the present invention. FIG. 3 is a schematic diagram of a data storage module 20 according to some embodiments of the present invention. The data storage system a1 may include a plurality of data storage devices 1 and a control apparatus 2. The data storage device 1 may be a data server for storing digital data. The control device 2 is electrically connected to the data storage apparatus 1 for controlling the data storage apparatus 1. In some embodiments, the control device 2 may be a computer.

A plurality of external electronic devices (not shown) can be connected to the data storage device 1 via the control device 2, and can transmit digital data to the data storage device 1 for storage or obtain digital data inside the data storage device 1. For example, the external electronic device may be a personal computer or a mobile device. The external electronic device can be connected to the data storage apparatus 1 via the internet.

The data storage device 1 includes a housing 10 and a plurality of data storage modules 20. The data storage module 20 is detachably disposed in the housing 10. Each data storage module 20 may include a housing 21, a plurality of storage devices 22, a plurality of fans 23, and a plurality of controllers 24. The storage device 22 is disposed in the housing 21. The housing 21 may be detachably provided in the housing 10. The storage devices 22 may be arranged in an array within the housing 21. In the present embodiment, the storage devices 22 can be arranged along an arrangement direction D1 and an arrangement direction D2.

Each storage device 22 may be a Hard-Disk Drive (HDD) or a Solid-State Disk (SDD) for storing digital data. For example, the physical structure of a rotating hard disk generally comprises a magnetic head, a disk, a main motor, an auxiliary motor, a main control chip, a bus cable, and other parts. When the main motor drives the disc to rotate, the auxiliary motor drives the magnetic head to the corresponding disc and determines to read the digital data on the disc. The magnetic head is suspended on the disk surface to draw a circular track concentric with the disk, and the magnetic field is positioned at a predetermined reading time or data interval by the magnetic coil of the magnetic head inducing the magnetism on the disk, thereby obtaining the data content of the magnetic field. When the storage device 22 is subjected to a large vibration, the data disc will shake, and the error rate of the storage device 22 during reading and writing is increased, so that the operation performance of the storage device 22 is reduced.

The fan 23 is disposed within the housing 21 proximate the rear side 211 of the housing 21. In the present embodiment, the fan 23 is adjacent to the storage device 22. The fans 23 are arranged along the arrangement direction D2, and the storage device 22 may not be located between the fans 23. Each fan 23 generates an airflow in the storage device 22 along the arrangement direction D1 to dissipate heat of the storage device 22. In the present embodiment, each fan 23 and the plurality of storage devices 22 may be sequentially arranged along the arrangement direction D1.

The controller 24 may be electrically connected to the storage device 22 and the fan 23. The controller 24 can be used to transmit digital data to the storage device 22 or transmit digital data inside the data storage apparatus 1 to an external electronic device. In some embodiments, the controller 24 may be a network card and a hard disk control card.

The control device 2 can be electrically connected to the controller 24 of each storage device 22, and control the connection speed of the storage device 22 and the rotation speed of the fan 23 via the controller 24. In some embodiments, the data storage system a1 has a plurality of control devices 2. Each control device 2 is electrically connected to the controller 24 in the corresponding storage device 22. In some embodiments, the control device 2 may be integrated into a separate controller 24.

When the storage device 22 in the data storage module 20 performs a large amount of data transmission, the storage device 22 generates a large amount of heat. In order to dissipate heat from the storage device 22, the rotation speed of the fan 23 is generally increased. However, the fan 23 may resonate with the housing when the rotation speed is increased. When the storage device 22 is a rotating hard disk, the vibration caused by the fan 23 greatly reduces the operation performance. The overall operation performance of the data storage module 20 can be improved by the following control method of the data storage system a1 according to the present invention.

FIG. 4 is a flow chart of a method of controlling data storage system A1 according to some embodiments of the present invention. It is understood that in the steps of the methods of the following embodiments, additional steps may be added before, after, and between the steps, and some of the steps may be replaced, deleted, or moved.

In the present embodiment, the following control method of the data storage system can be executed by a computer program product. In some embodiments, the computer program product may be loaded by a processor of the control device 2 to execute the control method of the data storage system. First, a setup phase of the control method of the data storage system a1 is performed. The setup phase may be performed after the data storage device 1 is built, or after the storage device 22 is replaced.

In step S101, the control device 2 obtains the type of each storage device 22. For example, the firmware of the storage device 22 stores specification parameters such as the model, type data, overheating number, rotation speed, transmission specification, etc. of the storage device 22. In this step, the control device 2 can read the firmware in each storage device 22 to obtain the specification parameters of the storage device 22, such as the type data. In the present embodiment, the storage device 22 may be a hard disk drive or a solid state drive.

In step S103, the control device 2 performs a performance test on the storage devices 22 and obtains a reference performance value of each storage device 22. In this embodiment, the performance test may be a read/write speed test, and the reference performance value may be a read/write speed. The control device 2 may test the amount of digital data that the storage device 22 can read and write per second. For example, the baseline performance value for one of the storage devices 22 may be 100 MB/s. In addition, when the storage device 22 is a solid state disk, the test of step S103 may not be performed, and the control device 2 may not need to obtain the reference performance value of the solid state disk. Since the solid state drive does not include a motor and a disk, the solid state drive is not directly affected by the vibration generated by the fan 23.

In step S105, the control device 2 queries internal parameters of each storage device 22 to obtain a threshold temperature value of each storage device 22. For example, the critical temperature value for one of the storage devices 22 may be 60 ℃. When the operating temperature of the storage device 22 exceeds 60 ℃, the storage device 22 may not operate normally or be damaged. Therefore, when the operating temperature of the storage device 22 exceeds 60 ℃, the storage device 22 will actively decrease the operating performance, thereby decreasing the temperature of the storage device 22.

In step S107, the control device 2 sets a position parameter for each storage device 22. The position parameter corresponds to the distance between the fan 23 and the storage device 22 in the arrangement direction D1. In some embodiments, the location parameter may be a positive integer. Table one is a comparison table of the storage device 22 and the location parameters in some embodiments, in comparison with the embodiment of fig. 3. The values 1 to 6 in table one represent the position parameters.

Watch 1

In the present embodiment, the storage devices 22 are defined as the first row R1 of storage devices 22, the second row R2 of storage devices 22, the third row R3 of storage devices 22, the fourth row R4 of storage devices 22, the fifth row R5 of storage devices 22, and the sixth row R6 of storage devices 22 according to the distance between the storage devices 22 and the fan 23 in the arrangement direction D1. For example, the distance between the storage devices 22 in the first row R1 and the fan 23 in the arrangement direction D1 is the shortest. The distance between the storage device 22 of the sixth row R6 and the fan 23 in the arrangement direction D1 is longest.

In the present embodiment, the data storage module 20 has six rows of storage devices 22, but the invention is not limited thereto. In some embodiments, the data storage module 20 may have more than three rows of storage devices 22. In addition, in the embodiment, the data storage module 20 has eight rows of storage devices 22, but the invention is not limited thereto. In some embodiments, the data storage module 20 may have more than three rows of storage devices 22.

In the present embodiment, the storage devices 22 closer to the fan 23 in the arrangement direction D1 have larger position parameters. For example, the position parameter of the storage device 22 of the first row R1 is 6. The position parameter for the storage device 22 of the second row R2 is 5. The position parameter for the third row R3 of storage devices 22 is 4. The position parameter for the storage device 22 of the fourth row R4 is 3. The position parameter for the storage device 22 of the fifth row R5 is 2. The position parameter for the storage device 22 of the sixth row R6 is 1.

In some embodiments, since each data storage module 20 is located at a different position within the data storage device 1, the position parameter can be adjusted according to the position of the data storage module 20 within the data storage device 1. For example, the location parameter may have a first location parameter and a second location parameter. The first position parameter corresponds to a distance between the storage device 22 and the fan 23 in the arrangement direction D1. The second location parameter corresponds to a location of the data storage module 20 within the data storage device 1.

In addition, since the data storage device 1 is located in different positions within the data storage system a1, the location parameter can be adjusted according to the position of the data storage device 1 within the data storage system a 1. For example, the location parameter further has a third location parameter. The third location parameter corresponds to the location of the data storage device 1 within the data storage system a 1.

FIG. 5 is a flow chart of a method of controlling data storage system A1 according to some embodiments of the present invention. After the setup phase is completed, the initial phase (step S201), the determination phase (steps S203 to S209) and the protection phase (step S211) of the control method of the data storage system a1 can be performed.

In step S201, the operation data storage system a1 starts to operate. In some embodiments, a plurality of external electronic devices may be connected to the data storage system a1 via the internet to enable the storage device 22 to operate.

In step S203, the control device 2 determines whether the storage device 22 is overheated. When the storage device 22 is overheated, step S205 is performed. When the storage device 22 is not overheated, step S207 may be executed. Generally, each storage device 22 has a temperature detecting function. For example, the storage device 22 may detect the operating temperature inside the storage device 22 by a temperature sensor. The control device 2 can be connected to the storage device 22 to obtain the operating temperature of the storage device 22.

In this embodiment, the control device 2 can obtain the operating temperature of each storage device 22 every time a predetermined time elapses. For example, the predetermined time may be 10 seconds, but is not limited thereto. When the operating temperature of one or more storage devices 22 exceeds the threshold temperature value, the control device 2 determines that the one or more storage devices 22 are overheated storage devices 22.

In step S205, the control device 2 increases the rotation speed of the fan 23 closest to the overheated storage device 22 in the arrangement direction D1 to prevent the overheated storage device 22 from abnormal operation or damage. For example, referring to table one and fig. 3, when only the first left storage device 22 in the second row R2 is overheated, the rotation speed of the fan 23a is increased, but the rotation speeds of the fans 23b, 23c, and 23d are not increased, so as to dissipate heat from the overheated storage device 22. Therefore, in the present embodiment, the resonance phenomenon can be avoided by avoiding increasing the rotation speed of all the fans 23a, 23b, 23c, 23d at the same time.

In some embodiments, the control device 2 can increase the rotation speed of the fan 23 by 10% for each step S205, so as to gradually increase the air volume generated by the fan 23. Therefore, the rotational speed of the fan 23 is prevented from being increased too fast at one time, and resonance is prevented from occurring in the data storage module 20. In this embodiment, step S207 can be executed after step S205 is executed. In other embodiments, the step S205 may be executed and then the process returns to the step S201 or the step S203.

In step S207, the control device 2 obtains the actual performance value of each storage device 22. In some embodiments, the actual performance value is the read/write speed of the storage device 22. For example, the actual performance value of one of the storage devices 22 may be 80 MB/s.

Then, the control device 2 obtains a performance comparison value of each storage device 22 according to the actual performance value of each storage device 22 and the reference performance value. In this embodiment, the performance comparison value may be a performance degradation rate. The performance comparison value of each storage device 22 can be obtained according to the difference between the reference performance value and the actual performance value of each storage device 22.

For example, the performance comparison value for each storage device 22 may be ((a-B)/a) × 100%, where "a" is a baseline performance value for one of the storage devices 22 and "B" is an actual performance value corresponding to the storage device 22. For example, the baseline performance value of the first storage device 22 to the left of the third row R3 is 100MB/s, and the actual performance value is 95 MB/s. The comparison of the performance of the first left side of the third row R3 is 5% as calculated by the above formula. In some embodiments, the above formula may be (A-B)/A.

Table two is a comparison table comparing the embodiment of fig. 3, the storage device 22 and performance comparison values in some embodiments. In Table two, the rotation speed of the fan 23 can be 10000 rmp. In table two, the larger the performance comparison value, the more the operation performance of the corresponding storage device 22 is decreased.

Watch two

In step S209, the control device 2 obtains a plurality of correlation coefficients corresponding to the storage device 22 according to the position parameters of the first table and the performance comparison values of the second table. In the present embodiment, the control device 2 calculates the correlation coefficient between the position parameters of the storage device 22 and the fan 23 in the arrangement direction D1 and the equivalent comparison value according to the conventional statistical formula (as shown in table two). In other words, each row of storage devices 22 corresponds to a correlation coefficient.

If the storage device 22 is affected by the resonance of the fan 23 and the operation performance is degraded, the closer the storage device 22 is to the fan 23 in the arrangement direction D1, the more the operation performance of the storage device 22 is degraded. Therefore, when the performance comparison value of the storage device 22 in the arrangement direction D1 has a positive correlation with the position parameter and the correlation coefficient is greater than a predetermined correlation value, it represents that the operation performance of the storage device 22 is decreased by the resonance of the fan 23, and step S211 can be performed. In this embodiment, the predetermined correlation value may be 0.6.

In the present embodiment, when the performance comparison value is positively correlated with the position parameter, the performance comparison value tends to be larger as the storage device 22 is closer to the fan 23 in the arrangement direction D1. For example, in the embodiment, the performance comparison value of the storage device 22 in the first row R1 is significantly greater than the performance comparison values of the storage devices 22 in the second row R2 to the sixth row R6, so that the performance comparison value and the position parameter show positive correlation.

When the performance comparison value of the storage device 22 in the arrangement direction D1 is negatively correlated with the position parameter, or the correlation coefficient is smaller than the predetermined correlation value, it indicates that the operation performance of the storage device 22 is not degraded by the resonance effect of the fan 23, and the process returns to step S201.

FIG. 6 is a flow chart of a method of controlling data storage system A1 according to some embodiments of the present invention. In step S209, when the operation performance of the storage device 22 is not decreased by the resonance of the fan 23, the operation performance may return to step S203. Therefore, in the present embodiment, the control device 2 can directly perform the step of determining whether the segment storage device 22 is overheated, so as to detect the operating condition of the data storage module 20 in real time.

In step S211, when the performance comparison value of the storage devices 22 in the arrangement direction D1 is positively correlated with the position parameter and the correlation coefficient is greater than the predetermined correlation value, the control device 2 adjusts the connection speed of one of the storage devices 22.

In some embodiments, the control device 2 can reduce the transmission specification of the storage device 22 to achieve the purpose of reducing the connection speed of the storage device 22. For example, the control device 2 may reduce the transmission specification SAS-4 of the storage device 22 to SAS-3, thereby reducing the connection speed of the storage device 22.

Generally, the vibration of the fan 23 affects the operation of the storage device 22. As the transmission speed of the storage device 22 is faster, the error rate (error rate) of the storage device 22 is likely to be greatly increased or even damaged due to the vibration effect and the lower fault tolerance of the storage device 22 for digital data transmission. Therefore, reducing the connection speed of the storage device 22 can reduce the error rate, and the reduction of the connection speed can reduce the rotation speed of the storage device 22, so as to change the resonance frequency of the storage device 22 and reduce the resonance effect caused by the vibration of the fan 23.

In some embodiments, the control device 2 may adjust the connection speed of the storage device 22 with the highest performance comparison value of the storage devices 22 in a row direction D1, such as the connection speed of the storage device 22 in the first row R1 in the table. In some embodiments, the control device 2 may decrease the connection speed of the storage device 22 closest to the fan 23, such as the connection speed of the storage device 22 in the first row R1 in the table.

When the connection speed of the storage device 22 is lower, the corresponding performance comparison value of the storage device 22 is improved. For example, in table two, the performance comparison of the first row R1 of storage devices 22 can be improved to a range of 10% to 60%, thereby improving the operating efficiency of the data storage module 20.

In some embodiments, the control device 2 may further adjust or reduce the rotation speed of the fan 23 in an arrangement direction D1 corresponding to the correlation coefficient being greater than the predetermined correlation value, so as to reduce the resonance of the fan 23. In some embodiments, the control device 2 can reduce the rotation speed of the fan 23 by 10% every time step S211 is executed, so as to avoid the risk that the rotation speed of the fan 23 is reduced too much at one time and the storage device 22 is overheated.

After the step S211 is completed, the operation performance of the data storage module 20 can be monitored in real time by returning to the step S201. In addition, the control device 2 can record the adjustment parameters of the related fans 23 and the storage device 22, so as to accelerate the adjustment speed of the data storage module 20 when a similar condition occurs in the data storage module 20.

In summary, the control device of the present invention can detect whether the operation performance degradation of the storage device is caused by the resonance of the fan. If the operating performance of the storage device is reduced due to the resonance of the fan, the connection speed of a part of the storage device can be selectively adjusted, or the rotating speed of the fan can be further adjusted, so that the overall performance of the data storage system is improved.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. Therefore, the above embodiments are not intended to limit the scope of the present invention, which should be determined by the following claims.