Patent Publication Number: US-9906424-B2

Title: Method and system for storage traffic modeling

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method and a system for storage traffic modeling. More particularly, the present invention relates to a method and a system for storage traffic modeling in a Software Defined Storage (SDS). 
     BACKGROUND OF THE INVENTION 
     Cloud services had been very popular in the recent decade. Cloud services are based on cloud computing to provide associated services or commodities without increasing burden on client side. Cloud computing involves a large number of computers connected through a communication network such as the Internet. It relies on sharing of resources to achieve coherence and economies of scale. At the foundation of cloud computing is the broader concept of converged infrastructure and shared services. Among all the shared services, memory and storage are definitely the two having maximum demand. This is because some hot applications, such as video streaming, require huge quantity of data to be stored. Management of memories and storages while the cloud services operate is very important to maintain normal service quality for the clients. 
     For example, a server used for providing cloud services usually manages or links to a number of Hard Disk Drives (HDDs). Clients access the server and data are read from or written to the HDDs. There are some problems, e.g. latency of response, due to limitation of the HDD system. Under normal operation of HDD system, the latency is usually caused by requirements of applications (i.e. workload), as the required access speed is higher than that the HDD system can support. In the past, latency might not be a problem since service providers of cloud service can offer infrastructure for the maximum capacity that can be expected. However, with more and more clients joining and sharing resources of the services, the fixed infrastructure may not be able to support the increasing requirement from the clients. To improve and strengthen the infrastructure, a flexible adjustment of the infrastructure is needed, in addition to only preparing more hardware. It is not economical to put all resources just for an unsure situation that might happen at a point of time in the future. 
     Another increasing demand as well as the cloud service is software defined storage. Software defined storage refers to computer data storage technologies which separate storage hardware from the software that manages the storage infrastructure. The software enabling a software defined storage environment provides policy management for feature options, such as deduplication, replication, thin provisioning, snapshots, and backup. With software defined storage technologies, the requirement of flexible adjustment of infrastructure can be fulfilled. Sufficient resources of the infrastructure can be used on time while unused hardware in the infrastructure can be standbys in order to save power consumption and prolong hardware life cycle. Besides the flexible adjustment of infrastructure, if the system can predict the storage traffic in the near future and adjust itself accordingly to match the requirements, the system can better serve the clients. In other words, it is high demand for a system being capable of predicting workload in a particular point in time in the future, and that is called traffic modeling. The storage traffic modeling is especially the main interest in this invention. 
     With reference to US Patent Publication No. 20090138420 which discloses a useful invention for the demand mentioned above. A method is for modeling network traffic in which an artificial neural network architecture is utilized in order to intelligently and adaptively model the capacity of a network. Initially, the network traffic is decomposed into a number of categories, such as individual users, application usage, or common usage groups. Inputs to one artificial neural network are then defined such that a respective combination of inputs permits prediction of bandwidth capacity needs for that input condition. Outputs of that artificial neural network are representative of the network traffic associated with the respective inputs. For example, a number of bandwidth profiles associated with respective categories may be defined. An artificial neural network is then constructed and trained with those bandwidth profiles and then utilized to predict future bandwidth needs for the network. 
     Application of artificial neural network for prediction of bandwidth profiles is the key portion in the invention. Detailed processes for implementing the invention are disclosed. However, the invention is basically used for prediction of bandwidth profiles for flights according to the embodiments. Under this situation, the infrastructure for the network traffic is almost fixed with just different workloads, e.g. passengers use the infrastructure from different group. Without linking to any cloud service, its hardware of infrastructure may be adjusted according to different workloads. Meanwhile, prediction of requirements of applications for a cloud service is not easily done by learning data from different categories. Precisely, the prediction should be made based on different performance parameters from one source. For example, by learning Input/output Operations Per Second (IOPS) of a hard disc drive (HDD) system and latency in a period of time in the past time to predict IOPS in the future. 
     Therefore, a new method and system for predicting storage traffic and providing a traffic modeling for a storage defined storage system based on an artificial neural network is still desired. 
     SUMMARY OF THE INVENTION 
     This paragraph extracts and compiles some features of the present invention; other features will be disclosed in the follow-up paragraphs. It is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims. 
     According to an aspect of the present invention, a method for storage traffic modeling in a Software Defined Storage (SDS) includes the steps of: collecting observed values of at least one performance parameter in a period of time from a storage node; learning a trend structure of the at least one performance parameter varying with time from the observed values; and providing a predicted value of one performance parameter in a particular point in time in the future. The storage node is operated by SDS software. The trend structure is adjusted based on observed values collected after the period of time. The predicted value is an output of the trend structure which has been adjusted. The performance parameter comprises Input/output Operations Per Second (IOPS), latency, throughput, and queue. 
     The method further includes the steps of: comparing one outputted predicted value with one compared observed value of the performance parameter in the particular point in time; and adjusting the trend structure so that another predicted value from the adjusted trend structure for the same particular point in time is closer to the compared observed value. 
     Preferably, the trend structure has a hidden element and an output element. The hidden element is constructed by using multiple nodes each built by finding out weights and a first bias value and setting a first activation function, and operated by multiplying the weights with the observed values or the predicted value, adding the results of multiplications to the first bias value as a sum, inputting the sum to the first activation function, and generating a transition value from the first activation function. The trend structure is adjusted by amending at least one of the weights, the first bias value, and/or parameters of the first activation function. In the present invention, the first activation function is a sigmoid function. However, practically it is not limited to the sigmoid function and can be other kind of functions, including linear function, tan h function, signum function, or step function. A suitable one will be used to have a best predicting result. 
     The output element is built by finding out a weight and a second bias value and setting a second bias value, and operated by multiplying the weight with the transition value of each neural node of the hidden element, adding the result of multiplication to the second bias value as a sum, inputting the sum to the second activation function, and generating the predicted value from the second activation function. Thus, the trend structure is adjusted by amending the weight, the second bias value and/or parameters of the second activation function. The second activation function is usually a linear function, but can be other kind of functions, including sigmoid function, tan h function, signum function, or step function. 
     According to another aspect of the present invention, a system for storage traffic modeling in a Software Defined Storage (SDS) includes: a traffic monitoring module, for collecting observed values of at least one performance parameter in a period of time from a storage node; and a neural network prediction module, learning a trend structure of the at least one performance parameter varying with time from the observed values and providing a predicted value of one performance parameter in a particular point in time in the future. The storage node is operated by SDS software. The trend structure is adjusted based on observed values collected after the period of time. The predicted value is an output of the trend structure which has been adjusted. The performance parameter comprises IOPS, latency, throughput, and queue. 
     The neural network prediction module further comparing one outputted predicted value with one compared observed value of the performance parameter in the particular point in time, and adjusting the trend structure so that another predicted value from the adjusted trend structure for the same particular point in time is closer to the compared observed value. Preferably, the trend structure has a hidden element and an output element. 
     The hidden element multiplies weights with the observed values or one predicted value from the output element, adding the results of multiplications to a first bias value as a sum, inputting the sum to the first activation function, and generating a transition value from the first activation function. 
     The output element multiplies a weight with the transition value of each neural node of the hidden element, providing a second bias value, adding the result of the multiplication to the second bias value as a sum, and inputting the sum to the second activation function. The trend structure is adjusted by amending the weigh, the second bias value, and/or parameters of the first or second activation function. In the present invention, the first activation function is a sigmoid function. However, it is not limited to the sigmoid function practically and can be other kind of functions, including linear function, tan h function, signum function, or step function. The second activation function is usually a linear function, but can be other kind of functions, including sigmoid function, tan h function, signum function, or step function. 
     The traffic monitoring module or neural network prediction module is hardware or software executing on at least one processor in the storage node. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of a method for storage traffic modeling according to the present invention. 
         FIG. 2  illustrates a system for storage traffic modeling in an embodiment according to the present invention. 
         FIG. 3  shows an architecture of a storage node. 
         FIG. 4  illustrates a trend structure in the system in an embodiment. 
         FIG. 5  depicts collected observed values for learning and predicted values by the system. 
         FIG. 6  illustrates another trend structure in the system in an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention will now be described more specifically with reference to the following embodiments. 
     Please refer to  FIG. 1  to  FIG. 4 . An embodiment is disclosed.  FIG. 1  is a flow chart of a method for storage traffic modeling according to the present invention.  FIG. 2  illustrates a system  10  applying the method in the embodiment. The system  10  can be used to predict performance parameters, such as Input/output Operations Per Second (IOPS), latency, throughput, and queue for a software defined storage (SDS) system in a network. 
     In this embodiment, the SDS system is a storage node  100 . The network may be internet. Thus, the storage node  100  may be a database server managing a number of storages and providing cloud services to clients. The storage node  100  may also be a file server or a mail server with storages for private use. The network can thus be a Local Area Network (LAN) for a lab or a Wide Area Network (WAN) for a multinational enterprise, respectively. Application of the storage node  100  is not limited by the present invention. However, the storage node  100  must be a SDS. In other words, the hardware (storage devices) of the storage node  100  should be separated from the software which manages the storage node  100 . The storage node  100  is operated by SDS software. Hence, reconfiguration of the storage devices in the storage node  100  can be available by individual software or hardware. Conventionally, the storage node  100  may be composed of a managing server  102 , a number of hard disc drives (HDD)  104  and solid state drives (SSD)  106  as shown in  FIG. 3 . The managing server  102  can receive commands to processes reconfiguration of the HDDs  104  and SSDs  106 . Therefore, only a portion of HDDs  104  and SSD  106  are used for specified requirements of applications i.e. workload). Power can be saved since the rest hardware of the system  10  is standby. The present invention can not only be applied to the storage node  100  with variable reconfiguration of storage, but also to a storage node with fixed infrastructure. 
     The system  10  includes a traffic monitoring module  120  and a neural network prediction module  140 . It should be noticed that the traffic monitoring module  120  or the neural network prediction module  140  is not limited to hardware only. They may be software executing on at least one processor in the storage node  100 . The neural network prediction module  140  can be operated based on any neural network technique. The present invention implements the neural network technique for SDS system to provide prediction of performance parameters so that a traffic modeling can be available. 
     The traffic monitoring module  120  is used to collect observed values of at least one performance parameter in a period of time from the storage node  100 . As mentioned above, the performance parameter may be an IOPS, latency, throughput, or queue in the storage node  100 . In this embodiment, observed values of one performance parameter, for example latency, are collected for learning by the neural network prediction module  140  and predicted values of latency, can be provided in a particular point in time in the future. According to the present invention, the observed values of performance parameter can be used to predict values of themselves in the particular point in time in the future. In another embodiment which will be described later, predicted values of multi-performance parameters can be used to predict values of one performance parameter in the particular point in time in the future. 
     Precisely, the neural network prediction module  140  learns a trend structure of the at least one performance parameter which varies with time from the observed values. Based on the results of learning, predicted values of one performance parameter are provided in a particular point in time in the future. As mentioned above, the observed values and the predicted values are both latency. The neural network prediction module  140  may compare one outputted latency with one compared observed value of latency in the particular point in time. It can adjust the trend structure so that another predicted value of latency from the adjusted trend structure for the same particular point in time is closer to the compared observed value. For example, when a latency predicted 30 seconds later is 2.0 seconds based on the observed values of latency during past 120 seconds, a compared latency 30 seconds later is 2.5 seconds. Thus, the trend structure must be adjusted. As inferred from the description above, the trend structure may be hardware or software executing on at least one processor in the storage node  100 . No matter what form it is, in order to have a better understanding, the trend structure is specified in  FIG. 4 . 
     As shown in  FIG. 4 , the trend structure includes a hidden element and an output element. The hidden element is constructed by using multiple neural nodes. Each neural node multiplies weights with the observed values or one predicted value from the output element. In this embodiment, there are two neural nodes in the hidden element. In fact, the number of neural nodes can be more than 2. More performance parameters can be used to predict one specified performance parameter in the future. This will be illustrated in another embodiment later. One neural node multiplies observed values of latency with a group of weights w 1  and the other multiplies predicted values of latency with a group of weights w 2 . Meanwhile, the hidden element can add the results of multiplications mentioned above to a first bias value, b 1 , as a sum and input the sum to the first activation function to generate a transition value from the first activation function. In the present invention, the first activation function is a sigmoid function. However, practically it is not limited to the sigmoid function and can be other kind of functions, including linear function, tan h function, signum function, or step function. A suitable one will be used to have a best predicting result. Thus, the output element can use the transition value for further calculation. 
     The output element multiplies a weight, w 3 , with the transition value of each neural node of the hidden element and provides a second bias value, b 2 . It adds the result of multiplication to b 2  as a sum, inputs the sum to the second activation function, and then generates the predicted value from the second activation function. The second activation function is usually a linear function, but can be other kind of functions, including sigmoid function, tan h function, signum function, or step function. 
     As mentioned above, the trend structure can be adjusted. The trend structure is adjusted by amending at least one of the weights, the first bias value, the second bias value and/or parameters of the first activation function or second activation function. Amended quantities may be chosen by experience or other calculations. Any method is possible as long as another predicted value from the adjusted trend structure for the same particular point in time is closer to the compared observed value. However, the trend structure must be adjusted based on observed values collected after the period of time. For this, another embodiment will be discussed later. Thus, the predicted value is an output of the trend structure which has been adjusted. 
     Come back to  FIG. 1 . According to the description above, a method for storage traffic modeling according to the present invention can be concluded. The method includes the steps of: collecting observed values of at least one performance parameter in a period of time from a storage node (S 01 ); learning a trend structure of the at least one performance parameter varying with time from the observed values (S 02 ); and providing a predicted value of one performance parameter in a particular point in time in the future (S 03 ). The method can be applied for the storage node is operated by SDS software. The trend structure can be adjusted based on observed values collected after the period of time. The predicted value is an output of the trend structure which has been adjusted. IOPS, latency, throughput, and queue are included in the performance parameter. 
     In order to get a more precise predicted value, the method further includes the steps of comparing one outputted predicted value with one compared observed value of the performance parameter in the particular point in time (S 04 ); and adjusting the trend structure so that another predicted value from the adjusted trend structure for the same particular point in time is closer to the compared observed value (S 05 ). 
     Based on the method, we can further define a hidden element and an output element in the trend structure. The hidden element is constructed by using multiple nodes each is built by finding out weights and a first bias value and setting a first activation function. It is operated by multiplying the weights with the observed values and the predicted value, adding the results of multiplications to the first bias value as a sum, inputting the sum to the first activation function, and generating a transition value from the first activation function. The output element is built by finding out a weight and a second bias value and setting a second bias value. It is operated by multiplying the weight with the transition value of each neural node of the hidden element, adding the result of multiplication to the second bias value as a sum, inputting the sum to the second activation function, and generating the predicted value from the second activation function. 
     In the embodiment, the first activation function is a sigmoid function and the second activation function is a linear function. They may be other kind of functions, including sigmoid function, tan h function, signum function, or step function. The trend structure is adjusted by amending at least one of the weights, the first bias value, the second bias value and/or parameters of the first activation function or second activation function. 
     According to the spirit of the present invention, the collected observed value and the predicted value can be of the same performance parameter. Another embodiment is used to illustrate this point. Please refer to  FIG. 5 . Observed values of latency in the past are collected and a trend structure is obtained. The observed values are collected from 0 th  second to 30 th  second. After learning, the neural network prediction module is able to provide prediction for latency in a particular point in time in the future. Let the predicted value is made for 31 st  second. After another observed value of latency on 31 st  second is obtained, the observed value is compared with predicted value. As mentioned above, the difference is used to adjust the trend structure. It may be the weights or any of the bias value is changed. On 32 st  second, another comparison and adjustment are keeping going on. After try and error, on the 50 th  second, the trend structure starts to predict latency after the 50 th  second. Of course, the time set in this embodiment, e.g. 31 st  second and 50 th  second, is not limited when the present invention is applied. It can be any time for any system. 
     Predicted values of latency from the trend structure are marked in dots in  FIG. 5 . OF course, the trend structure may safely provide an upper bound and a lower bound (shown by the dashed lines) for its prediction. User may have references for their use of the predicted values. It should be noticed that the trend structure is still learning and adjusting by newly collected observed values after the 50 th  second. Namely, learning and adjusting never stops after prediction begins. 
     According to the spirit of the present invention, observed values of multi-performance parameters can be collected to predict values of one performance parameter in the future. Meanwhile, weights of the hidden element may not necessarily multiply with the predicted value from the output element. Please refer to  FIG. 6 . There are two performance parameters, IOPS and latency, are used to predict latency in the future. The hidden element includes two neural nodes. One multiplies observed values of IOPS with a group of weights w 4  and the other multiplies observed values of latency with a group of weights w 5 . Then, the hidden element adds the results of multiplications mentioned above to a first bias value, b 3 , as a sum and inputs the sum to the first activation function to generate a transition value. In the embodiment, the first activation function is a sigmoid function or may be other kind of functions, including linear function, tan h function, signum function, or step function. The observed values of IOPS replace the predicted value from the output element in the embodiment mentioned above. Functions of the output element are not changed. The output element multiplies a weight, w 6 , with the transition value of each neural node of the hidden element and adds the result of multiplication to a second bias value, b 4  as a sum. It further inputs the sum to the second activation function and generates the predicted value from the second activation function. 
     While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.