Abstract:
Exemplary systems and methods for server management are provided. An exemplary system comprises a plurality of servers, with each server having the ability to access a database or, in some embodiments, be configured to perform a calculation, computation or make a determination of a particular value, values or other information. A communications network delivers queries to each server whereby a look-up table directs query processing by the servers. Further embodiments of the system feature a program logic controller for rebalancing the workload of the network servers. Exemplary methods of processing queries on the system comprise submitting a query to the network, communicating the query to each server in the network and each server looking-up on a look-up table the processing responsibilities of the servers in the network. The query is processed by the server having primary responsibility for processing the query while other the servers monitor query processing. Transmission of a query result to a user typically completes the process.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to computer networks, and more particularly to network server balancing and redundancy. 
         [0003]    2. Description of Related Art 
         [0004]      FIG. 1  shows a simplified architecture  100  for a prior art approach to network server management. Three servers are illustrated: server  110  containing a first segment of a database; server  120  containing a second segment of the database; and server  130  containing a third segment of the same database. Also illustrated in  FIG. 1  is communications network  140  responsible for transferring information between users  150  through  170  and one of the three servers responsible for responding to a particular query. 
         [0005]    The prior art approach to server management illustrated in  FIG. 1  suffers from several drawbacks. 
         [0006]    First, the entire database in  FIG. 1  is divided between three separate servers. No single server contains the entire database nor do segments of the database overlap amongst the servers. For example, in the case of a phone book database, server A ( 110 ) may comprise entries A thru H, server B ( 120 ) may comprise entries I through Q, and server C ( 130 ) may comprise entries R-Z. Accordingly, in the event one of the three servers illustrated in  FIG. 1  experiences a delay or failure, the other servers in the network are unable to respond on behalf of the failed server, because they lack the requisite data. As a result, certain responses to queries may be delayed or go unprocessed. 
         [0007]    Second, even if all of the servers in the illustrated network of  FIG. 1  stored the requisite data and received all queries, there is no mechanism for one server to monitor whether another server with responsibility for processing a query is actually processing the query. As a result, one server may have available processing capability going unutilized as that server is under the misconception that another server is processing the request. 
         [0008]    Third, the prior art architecture illustrated in  FIG. 1  is not scalable. Server limitations (e.g. processor speed or storage capacity) dictate the number of queries a server can process. Installation of additional servers to store additional information and process additional queries often requires shutting down an entire network. Additional downtime is often imposed by rearranging data on existing servers. Consequently, as evidenced by the prior art architecture illustrated in  FIG. 1 , there is a need for improved systems and methods of server management. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention provides exemplary systems and methods for server management. An exemplary system comprises a plurality of servers, each server having the ability to access a database. An exemplary communications network allows for queries to be received by all servers in the network, while a look-up table identifies the servers in the network responsible for processing particular queries. Further embodiments of the system feature a program logic controller for tracking and rebalancing the workload of the network servers. 
         [0010]    An exemplary method of server management comprises installing a copy of a database (or portion thereof) on each network server, receiving all queries at all servers, and processing queries as directed by a look-up table. 
         [0011]    An exemplary method of query processing comprises submitting a query to a network, sending the query to every server in the network and each server looking-up on a look-up table the server in the network having primary responsibility for processing the particular query. Monitoring of the processing of queries in the network is performed by all network servers. A query result may be transmitted to the user thereby completing the process. 
         [0012]    An exemplary method of rebalancing server load includes determining an overall query response rate for a network, comparing the overall query response rate for the network to a target overall query response rate, determining a query response rate for each server in the network, and comparing the query response rates for all of the servers in the network. Based on this method, the primary responsibility for one or more data segments can be transferred from one server in the network having a relatively slow query response rate to a server in the network having a relatively fast query response rate. This method can be performed either manually or with the support of an optional program logic controller. In the event server load is not rebalanced, further embodiments of the present invention include methods for introducing an additional server to the network. 
         [0013]    Exemplary methods of introducing an additional server to the network include installing a copy of the database (or portions thereof) used on the existing servers in the network on the additional server, configuring the additional server to receive all queries and installing a look-up table that either resides on or is accessible by the additional server to the network. Further embodiments include configuring the additional server to monitor the processing of queries in the network. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a simplified architecture of a prior art, non-scalable, non-redundant and failure-prone approach to network server management; 
           [0015]      FIG. 2  is an exemplary network architecture in which a scalable, redundant and reliable server network may be implemented; 
           [0016]      FIG. 3  is an exemplary look-up table according to one embodiment of the present invention; 
           [0017]      FIG. 4  is an exemplary look-up table according to an exemplary scenario of server load balancing; 
           [0018]      FIG. 5  is an exemplary look-up table according to an exemplary scenario of server load rebalancing by the addition of a server to the network; 
           [0019]      FIG. 6  is a flowchart for one exemplary method of establishing a scalable, redundant and reliable server network according to various embodiments of the invention; 
           [0020]      FIG. 7  is a flowchart for one exemplary method of processing a query on a scalable, redundant and reliable server network according to various embodiments of the invention; 
           [0021]      FIG. 8  is a flowchart for one exemplary method of rebalancing network server load either manually or by the use of a program logic controller according to various embodiments of the invention; and 
           [0022]      FIG. 9  is a flowchart for one exemplary method of rebalancing network server load by the installation of an additional server according to various embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Referring to  FIG. 2 , an exemplary network architecture  200  is illustrated in which various embodiments of the invention may be implemented. The exemplary network architecture  200  includes an optional program logic controller  202 , an optional master database  204  and a look-up table  300  ( FIG. 3 ). Optional communications linkage  206 , servers  208  through  218 , and communications network  220  also comprise the exemplary network architecture shown in  FIG. 2 . In some embodiments of the present invention, servers  208  through  218  each contain one or more clocks and/or other timing devices that are maintained in synchrony with one another and/or based upon each clock or other timing device periodically referencing a shared standard through communications network  220 , such as an atomic clock. Ultimately, some sort of a timing means (e.g., clock, timer, etc.) is necessary—as will be explained in detail herein—to ensure that a query has been timely handled by a primary server before the query is passed to a secondary server for handling (e.g., response). 
         [0024]    Certain timing devices may be better suited to particular configurations than others (although they are not necessarily prevented from being implemented in those configurations). For example, a clock may be best suited for a shared query resource (as described below) whereas a simple timer may be best suited for responding to individual queries delivered to the exemplary network architecture  200 . 
         [0025]    In  FIG. 2 , queries are generated by users  150  through  170  and communicated over communications network  220  to servers  208  through  218 . In one exemplary embodiment, communications network  220  uses multicast or broadcast techniques to communicate queries to the servers. In this exemplary embodiment, all servers receive all queries. Among other things, a query may comprise a request for the calculation, computation or determination of a particular value, values or other information. Queries may also comprise a request for a return of information, which may further comprise the aforementioned values or other information. In alternative embodiments, other wired and/or wireless mechanisms communicate all queries to all servers. In yet further embodiments, queries and/or notice of queries are communicated to a subset of servers comprising the network, wherein the servers that are not responsible for processing or backing up a particular query do not receive the query. In still further embodiments of the present invention, queries may be held in a shared resource, that resource comprising a list of outstanding queries, which can be monitored and/or accessed by the aforementioned network of servers. This shared resource may be an intermediate server, some sort of queuing mechanism (e.g., a router), a memory buffer or other means for maintaining a list of queries or the actual queries themselves. 
         [0026]    Communications network  220  allows each server in the exemplary network architecture  200  to monitor query processing by the other servers in the network. For example, a reply to a query may be broadcast or multicast over the network  200 . In alternative embodiments, other forms of server peer monitoring are used, such as optional communications linkage  206 . In still further embodiments, a subset of servers comprising the network are monitored by peer servers, wherein the servers that are not responsible for processing a particular query are not monitored. 
         [0027]    In an exemplary embodiment, servers  208  through  218  each contain an entire database or database copy. The contents of each database or database copy can be substantially the same or may have certain segments of data omitted. Alternative exemplary embodiments of the present invention include an optional master database  204 , which can be accessed by all of the servers in the network. Optional database  204  may be in lieu of or in addition to the entire database or database copy installed on each server. In the exemplary network architecture  200 , an entire database or database copy contains the information queried by users  150  through  170 . Database examples include telephone directories, customer databases or catalogs of products and/or services. Categories of other database content are within the scope of the present invention. In other embodiments of the present invention, servers  208  through  218  may be configured to process and/or respond to the aforementioned queries (e.g., be programmed with the necessary logic to respond to a particular calculation request). This configuration may be in addition to or in place of the aforementioned database or database copy. 
         [0028]    Each database or database copy comprises one or more segments of data or data segments. In some exemplary embodiments, segments of data are determined based on the nature of the underlying data. For example, the twenty-six letters of the English alphabet may represent twenty-six segments of data forming a telephone directory database. Twenty-six servers may each be assigned a primary responsibility for processing queries corresponding to a particular letter of the alphabet. For example, one server is assigned the primary responsibility for processing queries corresponding to last names beginning with the letter “A,” while a second server is assigned the primary responsibility for processing queries corresponding to last names beginning with the letter “B.” Likewise, a third server is assigned primary responsibility for processing queries corresponding to last names beginning with the letter “C,” and so on. 
         [0029]    In alternate embodiments, responsibilities for each server in a network may be determined based upon an arbitrary designation of data segments. For example, in some embodiments, a database may be segmented into as many equally-sized megabytes of data as there are servers forming the network. Various formulas may also be used to weight segment determinations based on averaging or estimating query frequency for a particular segment of the data or certain processing requirements related thereto. 
         [0030]    In an exemplary embodiment, segments of data in the database are manually or automatically cataloged by look-up table  300  ( FIG. 3 ). In an alternative embodiment, an optional program logic controller  202  may divide a database into optimized segments of data that are automatically updated and reflected in look-up table  300 . In an exemplary embodiment of the server network, program logic controller  202  monitors, balances and/or rebalances server load, based on factors such as changes in server usage, server storage capacity and/or query frequency. 
         [0031]    Turning to  FIG. 3 , exemplary look-up table  300  is shown. In accordance with some embodiments of the invention, a look-up table such as look-up table  300  directs query processing by network servers. The presence of columns and headers in look-up table  300  is for illustrative purposes and not meant to impose any particular data structure or format. 
         [0032]    In look-up table  300 , servers  208  through  218  ( FIG. 2 ) are identified in column  310 . In some embodiments of the present invention, each of these servers contains a copy of look-up table  300 . In alternative embodiments, the servers can access a centralized look-up table. 
         [0033]    Look-up table  300 , in column  320 , identifies the data segments installed in each of the servers. In the illustrated network architecture of  FIG. 2 , look-up table  300  reflects that an entire database comprising data segments  1 - 6  is installed in servers  208  through  218 . 
         [0034]    In exemplary embodiments, each server in a network is assigned one or more unique data segments. Collectively, each unique data segment assigned to each of the servers on the network comprises the entire database. The unique portion of the database or data segments represent that particular server&#39;s responsibility for processing when a query for information located in the server&#39;s unique data segment or segments is communicated to all of the servers on the network. In response to a query transmitted to all of the servers on the network, the particular server responsible for the data segment(s) containing the requested information will be allocated a certain amount of time to process the query while the other servers monitor the processing. Accordingly, the server first responsible for processing a query is deemed to have primary responsibility for processing queries for information located in the server&#39;s unique data segment(s). 
         [0035]    The primary responsibilities for each server in the network are identified in column  330  of look-up table  300 . As shown in  FIG. 3 , server  208  is assigned primary responsibility for data segment  1 ; server  210  is assigned primary responsibility for data segment  2 ; server  212  is assigned primary responsibility for data segment  3 ; server  214  is assigned primary responsibility for data segment  4 ; server  216  is assigned primary responsibility for data segment  5 ; and server  218  is assigned primary responsibility for data segment  6 . 
         [0036]    In look-up table  300 , each server is allocated  100  milliseconds in which to complete its assigned primary responsibility (e.g. responding to a query) as shown in column  340 . Exemplary look-up table  300  also includes an assigned time for secondary query initiation as reflected in column  370 . In the event a particular server assigned primary responsibility cannot process or respond to a particular query in its allocated time, a server having secondary responsibility is assigned a particular time to initiate the query. For example, should server  208  fail to respond within 100 milliseconds to a query of data segment  1  (for which server  208  has been assigned primary responsibility), server  210  will initiate processing of the same query following the expiration of server  208 &#39;s allocated primary response time (e.g. at 101 milliseconds as reflected in column  360 ). In some embodiments of the present invention, the assignment of a second query initiation time (col.  370 ) may not be necessary whereby a second server simply takes on processing responsibilities with the expiration of the allocated primary query response time (column  340 ) if there has not been a response to the query. 
         [0037]    In look-up table  300 , server  208  is assigned secondary responsibility for data segment  6 ; server  210  is assigned secondary responsibility for data segment  1 ; server  212  is assigned secondary responsibility for data segment  2 ; server  214  is assigned secondary responsibility for data segment  3 ; server  216  is assigned secondary responsibility for data segment  4 ; and server  218  is assigned secondary responsibility for data segment  5  as reflected in column  360 . In exemplary embodiments, secondary responsibility for querying a particular segment of data is not assigned to the same server having primary responsibility for the same segment of data, in order to enhance network reliability in the event of a server delay or failure. That is, the delay or failure of one server should not adversely impair the ability of a second server to step-in and respond to a particular query. 
         [0038]    Look-up table  300  indicates the exemplary server network is operating with double redundancy as reflected in column  350 . If the desired redundancy level indicates the server network is operating with double redundancy, a third server with tertiary responsibility will attempt to process any query missed by the respective primary and secondary servers. 
         [0039]    As illustrated by the exemplary look-up table  300 , tertiary responsibilities and respective query initiation times are assigned to server networks operating with double redundancy. In an exemplary embodiment, tertiary responsibility for querying a particular segment of data is not assigned to the same server having secondary responsibility for the same segment of data. Double redundancy enhances network reliability and performance in the event two servers experience a failure, because a third server can ‘step-in’ and process a query for a segment of data for which it has tertiary responsibility. 
         [0040]    According to some exemplary embodiments of the present invention, such as illustrated by exemplary network architecture  200 , the presence of optional master database  204  in addition to the database or database copy stored on each of servers  208  through  218  provides an additional fail-safe mechanism that can be accessed in the event each server with an assigned responsibility (i.e. primary, secondary, tertiary or so on) for a particular query should fail to process its assigned responsibility within the allocated. time. Provided the server containing optional master database  204  remains functional, no query should go unprocessed in such a network, because the server containing optional master database  204  will step-in and process the query or, alternatively, may be accessed by another capable server in the network to obtain, process and deliver the necessary data. 
         [0041]    Turning to  FIG. 4 , an exemplary look-up table according to an exemplary scenario of server load balancing is shown. Query response times, server usage, volume of stored data and query frequency are just a few of the reasons necessitating the balancing and/or rebalancing of server responsibilities and/or stored databases. An optional program logic controller  202  ( FIG. 2 ) can be used to monitor query response times, server usage, volume of stored data and/or query frequency and automatically rebalance a server network. In some embodiments, these adjustments are made manually. In either case, increased query response times are typically the first indication that a server network might be in need of rebalancing. One way of balancing and/or rebalancing a server network is illustrated by exemplary look-table  400 . In exemplary look-up table  400 , extra server storage capacity is created by the selective installation of data segments that comprise each server&#39;s database. 
         [0042]    The categories of information contained in look-up table  400  are similar to the categories of information contained in exemplary look-up table  300  ( FIG. 3 ), with the exception that column  420  reflects that each server in the network does not contain an entire copy of the database. Unlike the illustrative network reflected in exemplary look-up table  300 , segments of data are omitted from the data segments installed in the servers shown in column  420 . 
         [0043]    As illustrated in column  420  of exemplary look-up table  400 , data segments  1 - 2  and  4 - 6  are installed in server  208 . Data segment  3  is omitted from the database in server  208 . Server  208  is assigned primary responsibility for data segment  1  as shown in column  330 . Server  208  is also assigned secondary responsibility for data segment  6  (column  360 ), and assigned tertiary responsibility for data segment  5  (column  380 ). 
         [0044]    Additionally, as illustrated in column  420 , data segments  1 - 3  and  5 - 6  are installed in server  210 ; data segments  1 - 4  and  6  are installed in server  212 ; data segments  1 - 5  are installed in server  214 ; data segments  2 - 6  are installed in server  216 ; and data segments  1  and  3 - 6  are installed in server  218 . 
         [0045]    The exemplary scenario of server load balancing and/or rebalancing illustrated in exemplary look-up table  400  can be applied to the exemplary network shown in  FIG. 2  and  FIG. 3 , resulting in a savings of six data segments or the equivalent of the storage capacity of one server. As shown in column  350  of  FIG. 4 , the exemplary scenario of server load balancing and/or rebalancing retains the double redundancy level of the network. The extra server storage capacity can be used to store data segments transferred from servers experiencing a slow response time, as will be described in connection with  FIG. 7  herein. 
         [0046]    Turning to  FIG. 5 , an exemplary look-up table  500  whereby server load is rebalanced by the addition of a server to a network is shown. The categories of information contained in look-up table  500  are similar to the categories of information contained in exemplary look-up table  300  ( FIG. 3 ), with the exception that before server installation (columns  530  &amp;  570 ) and after server installation (columns  540  &amp;  580 ) comparisons are shown. 
         [0047]    As shown in  FIG. 5 , the database installed on each server remains the same throughout the installation process while the number of network servers and their responsibilities (i.e. primary, secondary and/or tertiary and so on) are changed. In column  520  of exemplary look-up table  500 , servers  208  through  218  each contain a database comprising data segments  1 - 50 . Data segments  1 - 50  have been installed in the additional server (titled “NEW”) prior to initiating server installation. Because each server contains a database comprising the same data segments, the network can continue operating while server NEW is added to the network. That is, the continuous operating of the network is not dependent on any one server. When server NEW is brought online, the before server installation settings (columns  530  &amp;  570 ) are replaced by the after server installation settings (columns  540  &amp;  580 ), and the network continues to operate uninterrupted. 
         [0048]    As an example of server load rebalancing by the installation of an additional server, assume in exemplary look-up table  500 , before the installation of server NEW, server  208 , server  210 , server  212 , and server  214  are each processing queries at an unacceptably slow rate. Also assume that server  216  is processing queries at an acceptable rate, and server  218  is processing queries at a maximum rate. As shown in column  560 , the network is operating at a single rate of redundancy or redundancy level. 
         [0049]    Server load rebalancing based on the exemplary method described in connection with  FIG. 8  herein will result in server  208  transferring primary responsibility for data segments  7 - 8  (column  530 ) to server  210  (column  540 ), server  210  transferring primary responsibility for data segments  14 - 17  (column  530 ) to server  212  (column  540 ), and server  212  transferring primary responsibility for data segments  21 - 26  (column  530 ) to server NEW (column  540 ). Likewise, server load rebalancing results in server  214  transferring primary responsibility for data segment  27  (column  530 ) to server NEW (column  540 ) and transferring primary responsibility for data segments  35 - 36  (column  530 ) to server  216  (column  540 ). Finally, server  216  transfers primary responsibility for data segments  42 - 43  (column  530 ) to server  218  (column  540 ). 
         [0050]    As evidenced by comparing the number of data segments for each network server before installation (column  530 ) to after installation (column  540 ), primary responsibility for server  208  decreases by two data segments; primary responsibility for server  210  decreases by two data segments; primary responsibility for server  212  decreases by two data segments and primary responsibility for server  214  decreases by three data segments. In total, the workload of these four servers decreases by nine data segments. After the installation of server NEW, primary responsibility for server  216  remains unchanged and primary responsibility for server  218  increases by two data segments. Finally, primary responsibility for server NEW is initiated with seven data segments (column  540 ). As shown in column  560 , the network remains operating at a single rate of redundancy. 
         [0051]    Turning to  FIG. 6 , an exemplary flowchart for one method of establishing a scalable, redundant and fault-tolerant server network according to an exemplary embodiment of the present invention is shown. 
         [0052]    At step  602 , an optional program logic controller  202  ( FIG. 2 ) is installed as part of the exemplary network architecture  200  ( FIG. 2 ). In an exemplary embodiment of the server network, program logic controller  202  monitors and rebalances server load, based in part on changes in server usage, server storage and query frequency. Optional program logic controller  202  reduces the need for network manual server maintenance and associated equipment upgrades and purchases, through automating, for example, the aforementioned functions. 
         [0053]    At step  604 , a database is installed on each server in the exemplary network architecture  200 . The contents of each installed database or installed database copy can be substantially the same or may have certain segments of data omitted. Database examples include but are not limited to telephone directories, customer databases or catalogs of products and/or services. 
         [0054]    At step  606 , an optional master database  204  ( FIG. 2 ) is installed in the server network. Optional master database  204  may be accessed by all of the servers in the network should such access ever prove to be necessary. 
         [0055]    At step  608 , network servers in the exemplary network architecture  200  are configured to receive all queries. In exemplary embodiments, communications network  220  uses multicasting or broadcasting to communicate all queries to all servers. In these embodiments, all servers receive all queries. In alternative embodiments, other wired and/or wireless mechanisms communicate all queries to all servers. In yet further embodiments, queries and/or notice of queries are communicated to a subset of servers comprising the network, wherein the servers that are not responsible for processing a particular query do not receive the query. 
         [0056]    At step  610 , a look-up table  300  ( FIG. 3 ) is installed for each of servers  208  through  218  ( FIG. 2 ) that comprise the exemplary network architecture  200 . In exemplary embodiments, look-up table  300  directs server query processing. Look-up-table  300  may be local or remote relative to the server  208  through  218 . 
         [0057]    At step  612 , a server redundancy level may be established for exemplary network architecture  200 . Server redundancy level is a function of the tolerance for server network failure. The lesser the tolerance for server network failure, the higher the server redundancy level. For example, users that can tolerate an occasional network failure might establish a single redundancy level as shown in  FIG. 5 , whereas users that can not tolerate an occasional network failure might establish a double redundancy level as shown in  FIG. 4 . As illustrated by exemplary look-up table  300 , a single redundancy level signifies that if a server assigned primary responsibility fails to process an assigned query within an allocated period of time, another server with secondary responsibility for the same segment of data will attempt to process the query. A double redundancy level signifies that a third server assigned tertiary responsibility will attempt to process any query missed by the servers assigned primary and secondary responsibilities. Assuming the installation of an entire database on each network server as illustrated in  FIG. 2 ,  FIG. 3 , and  FIG. 5 , the redundancy level of a server network is limited only by the number of servers (e.g. servers  208  through  218 ) on the network. 
         [0058]    At step  614 , servers comprising the exemplary network architecture  200  are configured upon receipt of each query to check the look-up table installed at step  610 . In exemplary embodiments, look-up table  300  identifies the data segments installed in each server. 
         [0059]    At step  616 , servers comprising the exemplary network architecture  200  are configured to process queries per look-up table  300 . Look-up table  300 , in the present example, allocates each server 100 milliseconds in which to complete its assigned primary responsibility. 
         [0060]    At step  618 , servers comprising the exemplary network architecture  200  are configured to monitor query processing by the other servers in the network. In exemplary embodiments, communications network  220  allows each server in the exemplary network architecture  200  to monitor query processing by the other servers in the network by ‘listening,’ for example, for a broadcast or multicast reply to the query. In alternative embodiments, other forms of server peer monitoring are used, such as optional communications linkage  206 . In yet further embodiments, a subset of servers comprising the network are monitored by peer servers, wherein the servers that are not to be responsible for processing a particular query are not monitored. 
         [0061]    At step  620 , servers comprising the exemplary network architecture  200  are configured to transmit query results to users. 
         [0062]    At step  622 , servers comprising the exemplary network architecture  200  are configured to reset upon transmission of a query result to a user. That is, present response time is reset to zero. 
         [0063]    Turning to  FIG. 7 , a flowchart for an exemplary method of processing a query on the exemplary network architecture  200  ( FIG. 2 ) is shown. 
         [0064]    At step  710 , a query is submitted to exemplary network architecture  200 . In the case of a server network for a telephone directory database, user  150  ( FIG. 2 ) submits a query for an address corresponding to a person having the last name of Jones. 
         [0065]    At step  720 , the submitted query is communicated to network servers. Here, the query for an address corresponding to a person having the last name of Jones is multicast through communications network  220  ( FIG. 2 ) to all servers in the exemplary network architecture  200 . 
         [0066]    At step  730 , the identity of the server having primary responsibility for processing the submitted query is determined based upon referencing a look-up table. Here, the look-up table for the queried telephone directory database reflects that the tenth server of twenty-six servers (each corresponding to a letter of the alphabet) is assigned primary responsibility for processing queries corresponding to last names beginning with the letter “J.” Therefore, server ten has the primary responsibility of querying its data segment for the address of Jones. 
         [0067]    At step  740 , the submitted query is processed (or attempted to be processed) by the responsible server. In this particular case, server ten processes the query for the address corresponding to Jones. 
         [0068]    At step  750 , the processing of the submitted query by the server having primary responsibility is monitored by the other servers in the network. In exemplary embodiments, communications network  220  allows each server in the exemplary network architecture  200  to monitor query processing by the other servers in the network through, for example, listening for a multicast or broadcast reply to the query. In alternative embodiments, other forms of server peer monitoring are used, such as through optional communications linkage  206 . In yet further embodiments, a subset of servers comprising the network are monitored by peer servers, wherein the servers that are not to be responsible for processing a particular query are not monitored. In this particular example, twenty-five of the twenty-six servers comprising the server network for the telephone directory database monitor the processing by server ten for the address corresponding to Jones. 
         [0069]    At step  760 , it is determined whether the submitted query has been processed within the allocated time. Referring to look-up table  300  ( FIG. 3 ), each server is allocated 100 milliseconds in which to complete its assigned primary responsibility. In this particular example, server ten determined within 100 milliseconds that the address corresponding to Jones is 2200 Geng Road, Palo Alto, Calif. 
         [0070]    At step  770 , should the query not be processed within the allocated time by the server having primary responsibility for the query (e.g. due to server delay or server failure), a server with secondary responsibility is determined based on the method described in connection with step  730 . The server with secondary responsibility then processes the query as set forth in steps  740 - 750 . Other backup and/or secondary servers continue to await an indication the query has been timely processed in step  760 . 
         [0071]    At step  780 , the query result is transmitted to the user who submitted the query via, for example, a multicast or broadcast methodology. In this particular example, user  150  ( FIG. 2 ) will receive the address for Jones via a multicast transmission over communications network  220 . 
         [0072]    At step  790 , network servers reset for the next query. In this particular example, the twenty-six servers comprising the telephone directory database will reset their present processing time to zero in anticipation of the next query to be submitted by a user. That is, the network servers await the arrival of a new query wherein overall processing time with regard to a particular query begins relative that particular query and its own timestamp (i.e., the overall time since the query was made or was received by the network servers). 
         [0073]    Turning to  FIG. 8 , a flowchart for one exemplary method of evaluating and rebalancing network server load according to an exemplary embodiment of the invention is shown. All steps in  FIG. 8  can be performed either manually or with the assistance of an optional program logic controller  202  ( FIG. 2 ). 
         [0074]    At step  810 , an overall network query response rate is determined. For example, the average time it takes to process each query submitted to the exemplary network architecture  200  ( FIG. 2 ) can be determined for a twenty-four hour period either manually or by an optional program logic controller  202 . Various other time periods or measures of response time may be used. 
         [0075]    At step  820 , the overall network query response rate as determined by step  810  is compared to a target overall network query response rate. For example, with respect to the telephone directory database described in connection with  FIG. 7 , the particular telephone company responsible for the telephone directory database might determine, on average, it desires to have all queries processed within 100 milliseconds. This comparison represents a measure by which the server network can be evaluated apart from the performance of the constituent servers. 
         [0076]    At step  830 , individual server query response rates are determined. For example, the average time it takes each of servers  208  through  218  in  FIG. 2  to process each query submitted in the exemplary network architecture  200  can be determined for a twenty-four hour period either manually or by an optional program logic controller  202  or through various other periods and measures of time. 
         [0077]    At step  840 , the response rates for all of the servers are compared. For example, in the exemplary embodiment illustrated in  FIG. 5  and described herein, the response rates of server  208 , server  210 , server  212 , and server  214  were slower than the response rates of server  216  and server  218 , which indicated that servers  208  through  214  warranted a reduction in the number of data segments for which they had primary responsibility. 
         [0078]    At step  850 , the primary responsibilities for particular data segments are transferred from the servers having slower query response rates to the servers having faster query response rates. For example, as described in connection with  FIG. 5 , server  208  transferred primary responsibility for data segments  7 - 8  (two data segments) to server  210 , server  210  transferred primary responsibility for data segments  14 - 17  (four data segments) to server  212 . 
         [0079]    At step  860 , an overall network query response rate is re-determined in the same fashion as described in connection with step  810 . 
         [0080]    At step  870 , the re-determined overall network query response rate as determined at step  860  is re-compared to the target overall network response rate. 
         [0081]    At step  880 , a decision is made as to whether the performance of the rebalanced server network measures favorably against the target network response rate. If the performance of the rebalanced server network is satisfactory, the overall network query response rate can be periodically re-determined, as described in connection with step  810 . If the performance of the rebalanced server network is not satisfactory, then step  890  may need to be undertaken. 
         [0082]    At step  890 , an additional server is installed in the server network, as described in connection with the exemplary method shown in  FIG. 9 . 
         [0083]    Turning to  FIG. 9 , a flowchart for an exemplary method of rebalancing network server load by the installation of an additional server is shown. 
         [0084]    At step  902 , a database or database copy corresponding to the database used in the existing server network is installed on the additional server. 
         [0085]    At step  904 , an optional master database  204  ( FIG. 2 ), is made accessible to the additional server to the network. This optional master database may have previously been made available to all other servers in the network. 
         [0086]    At step  906 , the additional server is configured to receive all queries submitted to the server network. In the example shown in  FIG. 2 , user queries are directed through communications network  220  ( FIG. 2 ) to all servers in the network. In yet further embodiments, queries and/or notice of queries are communicated to a subset of servers comprising the network. 
         [0087]    At step  908 , a look-up table, such as exemplary look-up table  500  ( FIG. 5 ), is either installed on the additional server or made accessible to the additional server. As shown in column  510  of exemplary look-up table  500 , the look-up table reflects the presence of the additional server. 
         [0088]    At step  910 , the additional server to the server network is configured to check the modified look-up table described in step  908 . 
         [0089]    At step  912 , the additional server to the network is configured to process queries. 
         [0090]    At step  914 , the additional server to the network is configured to monitor query processing by the other servers in the network. 
         [0091]    At step  916 , the additional server to the network is configured to transmit query results to the user. 
         [0092]    At step  918 , the additional server to the network is configured to reset its present response time in preparation for the next query to be submitted over the network. 
         [0093]    The present invention is described above with reference to exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made and other embodiments can be used without departing from the broader scope of the present invention. Therefore, these and other variations upon the exemplary embodiments are intended to be covered by the present invention.