Patent Publication Number: US-6990593-B2

Title: Method for diverting power reserves and shifting activities according to activity priorities in a server cluster in the event of a power interruption

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to systems and methods for server cluster power management, and more particularly for quality of service based server cluster power management. 
     2. Discussion of Background Art 
     A modem trend in network management is to an “always-on” model. Such a model recognizes the pervasiveness of computers and information within everyday business and personal activities. 
     To manage such growing demands, large data centers consisting of many clients and servers are networked together in clusters. Such clusters may be configured to provide various redundant and high availability processes and services. Unfortunately however, such clusters are still susceptible to power outages, which can bring all network traffic to a halt. 
       FIG. 1  is a block diagram of a conventional server cluster system  100  both before and after a power interruption at time T 0 . The conventional cluster  100  includes four servers  102 - 108 , coupled respectively to four Uninterruptible Power Supplies (UPSs)  110 – 116 , and which receive standard wall outlet power over line  118 . Each UPS typically contains a battery backup (not shown) which provides power to its respective server upon detection of a power interruption and for a period thereafter until the batteries are exhausted. 
     As shown in  FIG. 1 , at time T 0 , all four servers  102 – 108  are fully operational. However, if a power interruption occurs at time T 0 , there is a complete failure of the server cluster at time T 1 , when the UPS batteries have been exhausted. Thus all processes supported by the servers  102 – 108  are terminated and the network is down. Such a complete failure is indiscriminant of the importance of any traffic passing through or processes being executed by the servers, and is very much an “all or nothing” power management design. Such designs fall short of client expectations and network demands in this modern era. 
     In response to the concerns discussed above, what is needed is a system and method for server cluster power management that overcomes the problems of the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention is a system and method for Quality of Service (QoS) based server cluster power management. The method of the present invention includes the steps of: grouping activities within a server cluster into predefined sets; assigning a priority level to each set; identifying a first server hosting a first set of lower-priority activities within the cluster; receiving a power interruption signal; and diverting power reserves of the first server to another server in the cluster, in response to the power interruption signal. 
     The system of the present invention includes: servers, hosting a plurality of activity sets each having an associated QoS level; power reserves coupled to the servers; a switch matrix coupled to direct the power reserves between the servers; and a power manager, coupled to the switch matrix, for commanding the switch matrix to divert power from servers hosting low QoS activity sets to servers hosting high-priority activity sets, in response to a power interruption. 
     The system and method of the present invention are particularly advantageous over the prior art because QoS concepts are applied to server cluster power management. These and other aspects of the invention will be recognized by those skilled in the art upon review of the detailed description, drawings, and claims set forth below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a conventional server cluster system; 
         FIG. 2  is a block diagram of a Quality of Service (QoS) based server cluster power management system; 
         FIG. 3  is a flowchart of a method for Quality of Service based server cluster power management; 
         FIG. 4  is a block diagram of one of many possible ways to manage power in the server cluster in response to a power interruption; 
         FIG. 5  is a graph of how a power interruption affects available server cluster power in both the QoS based system and the conventional server cluster system; and 
         FIG. 6  is a graph of how a power interruption affects QoS in both the QoS based system and the conventional server cluster system. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 2  is a block diagram of a Quality of Service (QoS) based server cluster power management system  200 . The system  200 , shown in just one of many possible embodiments, includes servers  1  through  4  ( 202 – 208 ), each provided power by Uninterruptible Power Supplies (UPSs)  1  through  4  ( 210 – 216 ) respectively. A standard power line  218  provides wall outlet power to each of the UPSs  210 – 216 . Batteries within each UPS are connected to a power divert line  220 . The power divert line  220  is coupled to a switch matrix  222  which can divert battery power from a set of UPSs to any other set of UPSs. A power manager  224  software module, executing power management algorithms, is coupled to the switch matrix  222  and the UPSs  210 – 216  by a System Network Management Protocol (SNMP) line  226 , and to the servers  202 – 208  by a Quality of Service (QoS) line  226 . The power manager  224  and the switch matrix  222  are preferably housed in a power controller  230 . Together these elements make up a server cluster network. Operation of the system  200  is discussed in  FIG. 3 . 
       FIG. 3  is a flowchart of a method  300  for Quality of Service (QoS) based server cluster power management. Quality of Service (QoS) is a standard phrase originating from an idea that client-server network performance, such as transmission and error rates, can be managed in real time. And, while such QoS concepts have been applied to network packet switching and data management, they have not been applied to diverting power between different servers within a server cluster. 
     The method begins in step  302 , where a network administrator groups server activities into predefined sets. The predefined sets are defined by the network administrator depending upon how the administrator intends to manage power reserves within the network after a power interruption occurs. Examples of such predefined sets include: types of data transmitted by each of the servers  202 – 208  over the network; processes and applications, redundant or otherwise, executing on each of the servers  202 – 208 ; or any other useful differentiation of activity on the servers  202 – 208 . Data types include: voice, video, and bulk data. Processes and applications include: e-mail, word processing, virus detection, firewalls, daemons, as well as many others. 
     In step  304 , the network administrator assigns a QoS level to each set. Activity sets assigned a higher QoS can also be thought of as having a higher operational priority level. In step  306 , the power manager  224  monitors server activities and the QoS level assigned to each set of server activity over QoS line  228 . QoS levels are transmitted over the QoS line  228  preferably follow a Common Open Policy Service Protocol (COPS). COPS is a protocol for exchanging QoS information over a network. COPS protocols are discussed in an Internet-Draft working document generated by the Internet Engineering Task Force (IETF). In step  308 , the power manager  224  generates a priority list, organizing server activities based on their assigned QoS levels. 
     In step  310 , one or more of the UPSs  210 – 216  detect a power interruption on the standard power line  218 . In response, a power interruption signal is sent from the UPS&#39;s  210 – 216  to the power manager  224  over the SNMP line  226 , in step  312 . Next, in step  314 , the power manager  224  sends a server shutdown command to one or more of the UPSs  210 – 216  over the SNMP line  226 . 
     The power manager  224  selects which of the servers  202 – 208  to shutdown based on the priority list. How exactly the shutdown selections are made, however, is dependent upon how the network administrator programs the power manager  224  to respond to the power interruption signal. For example, the network administrator can program the power manager  224  to identify the server hosting an activity which is highest on the priority list and shutdown all other servers. Or, the network administrator can program the power manager  224  to identify the top five activities on the priority list, command the servers  202 – 208  to inactivate all other activities on the priority list and transfer those five highest priority activities to a single server and shutdown the other servers. Thus, cluster power management is under full control of the network administrator. Those skilled in the art will also recognize that the present invention provides an ability to divert power between servers for reasons not even related to power interruptions, but instead for any power management reason. 
     In step  316 , the power manager  224  sends a divert battery power command to the switch matrix  222 , directing the matrix  222  to reroute reserve battery power from those UPSs sent the server shutdown command to those UPSs powering those servers which remain operational. After step  316 , the method  300  ends. 
       FIG. 4  is a block diagram  400  of one of many possible ways to manage power in the server cluster in response to the power interruption on the standard power line  218 . In the Figure, the power manager  224  has commanded: UPS  2   212  to shutdown server  2   204 , UPS  3   214  to shutdown server  3   206 , UPS  2   216  to shutdown server  2   208 , and the switch matrix  222  to route reserve battery power from UPSs  1 ,  2  and  3  ( 212 ,  214 , and  216 ) to UPS  1   210  so that server  1   202  can be kept operational for as long as possible during the power interruption. 
       FIG. 5  is a graph  500  of how a power interruption, at time T 0 , affects available server cluster power  502  in both the QoS based system  200  and the conventional server cluster system  100 . As shown by curve  504 , when a power interruption occurs at time T 0  in the conventional system  100 , a step-wise complete power failure of servers  1  through  4  ( 102 – 108 ) occurs at time T 1 , as battery reserves in the conventional system&#39;s  100  UPSs  110 – 116  are exhausted all at about the same time. Total system  100  battery reserves are equal to an area under curve  502 . 
     In contrast, as shown by curve  506 , when a power interruption occurs at time T 0  in the QoS based system  200  and servers  2  through  4  ( 204 – 208 ) are shutdown and battery reserves in UPSs  212 – 216  are diverted to server  1   202 , server  1 &#39;s  202  time of operation is extended to a time T 2 , which is far beyond time T 1 . 
     Thus while total QoS system  200  battery reserves (equal to an area under curve  504 ) are equal to total conventional system  100  battery reserves, the present invention manages that same limited reserve of battery power so that server  1 &#39;s  202  operation may be extended until time T 2 . As a result, those activities highest on the priority list may continue servicing the cluster network beyond that of conventional systems  100 . 
       FIG. 6  is a graph  600  of how a power interruption, at time T 0 , affects QoS  602  in both the QoS based system  200  and the conventional server cluster system  100 . As shown by curve  604 , when a power interruption occurs at time T 0  in the conventional system  100 , a step-wise complete shutdown of all activities on servers  1  through  4  ( 102 – 108 ) occurs at time T 1 , as battery reserves in the conventional system&#39;s  100  UPSs  110 – 116  are exhausted all at about the same time. 
     In contrast, as shown by curve  606 , when a power interruption occurs at time T 0  in the QoS based system  200  and servers  2  through  4  ( 204 – 208 ) are shutdown and battery reserves in UPSs  212 – 216  are diverted to server  1   202 , server  1 &#39;s  202  overall Quality of Service for hosted high-priority activities is extended until time T 2 . The curve  606  also shows that, depending upon how QoS, is measured QoS may initially dip below QoS for the conventional system  100 , at time T X , QoS is basically maintained at a constant level all the way until time T Y , in the QoS based system  200 . Depending upon how the network administrator configures the power manager  224 , the initial dip can be due to a shutdown of lower-priority activities that can not be maintained on server  1   202 , while the conventional system  100  continues to host all activities. The somewhat graceful decline in QoS from time T 0  until T 2  is again determined by how the network administrator configures the power manager  224 , and can be due to the power manager  224  incrementally shutting down lower-priority server activities as power reserves dwindle. 
     While one or more embodiments of the present invention have been described, those skilled in the art will recognize that various modifications may be made. Variations upon and modifications to these embodiments are provided by the present invention, which is limited only by the following claims.