Abstract:
A storage controller for redundant arrays of independent disks (RAID) comprises a daughter card containing a standardized controller core, which is mated to one of a number of customizable controller interface cards. The controller core card includes high performance elements such as a processor, cache memory, CRC circuitry, a host port, and a storage port. All operational communication with non-core components occurs via the host port and the storage port through the controller interface card. The controller core card monitors and configures communications between the host and the storage array. Each controller interface card is populated with components and connectors particular to the respective application or RAID system. The size and layout of the controller interface card may also be customized to the particular application. Sharing the same controller core card among various RAID controllers lowers the cost and time-to-market for customized RAID systems.

Description:
BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates to the field of storage controllers and more particularly to storage controllers for redundant disk arrays. 
     2. The Relevant Art 
     Modern computer networks and systems require reliable means for the storage of data. For example, the wide-spread usage of online databases for conducting transactions and data retrieval has increased the demand for large data stores with non-stop, low-latency access. Various systems using redundant arrays of independent disk drives (RAID) have been developed and deployed in response to this need. 
     Customer requirements for RAID systems are highly application dependent. RAID systems vary in their interconnection architectures, physical packaging and dimensions, redundancy methods, fail-safe mechanisms, and the like. The disk drives available for use within RAID systems are also vary in their physical specifications, storage capacities, performance capabilities, and electrical interface. Due to the non-standardization in the aforementioned areas, a great deal of flexibility is required of RAID controllers. 
     As with many computing devices, much of the flexibility required of RAID controllers is achieved using configuration options stored in some type of non-volatile memory. The control software reads the configuration options, makes appropriate adjustments within peripheral devices and components, and changes its program flow to accomplish the desired behavior. As a consequence, much of the development cost of a RAID controller lies in the development of the control processor and associated firmware. 
     Another costly area of development is the architecting, characterizing and testing of the high bandwidth data paths that largely determine the performance of a RAID controller. The key performance metrics of access latency, throughput and reliability are directly affected by the design of these data paths. Due to these and other issues, the cost of re-architecting and redesigning a RAID controller for each possible system is prohibitive. 
     In contrast to the advanced features, high performance and flexibility required of RAID controllers, another key requirement is low cost. Many RAID systems use redundant controllers to increase reliability. The cost of the RAID controller may have a significant impact on the overall system cost. Entry level RAID systems are particularly price sensitive and must maintain a low cost per gigabyte of storage even with relatively small arrays of storage devices. Reducing the cost of key components, for example by making volume purchases without accumulating unneeded inventory, is crucial to lowering the cost of a RAID controller. 
     Another factor contributing to the cost of RAID systems is the opportunity cost associated with time-to-market. The inability to meet rising demand of a new product or market segment may significantly reduce or entirely eliminate prospective profits. Being the first to market with the right combination of features, price and performance is crucial for market success and the long term prospects of manufacturers of RAID systems. 
     What is needed is a mechanism to develop and customize a RAID controller quickly and at a low cost. Such a mechanism should facilitate cost effective procurement practices, reduce the time to market for new products, and leverage the high development and component cost of the core elements of a RAID controller. 
     OBJECTS AND BRIEF SUMMARY OF THE INVENTION 
     The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available RAID controllers. Accordingly, it is an overall object of the present invention to provide an improved method and apparatus for customizing and deploying a RAID controller that overcomes many or all of the above-discussed shortcomings in the art. 
     To achieve the foregoing object, and in accordance with the invention as embodied and broadly described herein in the preferred embodiments, an apparatus and method for customizing and deploying a modular RAID controller is provided wherein the functionality and components of a RAID controller are partitioned into a controller core card and a controller interface card. 
     The controller interface card contains those components and features that are generally unique to a particular customer or product such as I/O connectors, power control including battery backup, status indicators, hot swap features, configuration options and the like. The controller interface card is designed to match the physical constraints and form factor of a particular product or manufacturer. Design and development of these features are typically low-cost, straightforward and well known in the art. Generally, these features may be developed and produced as needed without significantly impacting delivery schedules and production costs. 
     The controller core card contains those components associated with costly development and production such as control processor, storage cache, XOR function, and channel controllers. These are also typically the components that are most easily standardized over a broad variety of systems and applications. Overall product cost is minimized by designing, developing, manufacturing and stocking a single common controller core card that is standardized across many RAID systems and their various form factors and value added features. Inventory costs are minimized and forecasting errors offset by using the same controller core card for multiple customers or product lines. 
     In one embodiment, the controller core card is a daughter card that mates with the controller interface card via a storage connector and a host connector. The storage connector and the host connector provide physical and electrical connectivity between the controller core card and the controller interface card. 
     In the preferred embodiment, the signals carried by storage and host connectors are selected to minimize the complexity of interfacing the controller core card with the controller interface card. The storage connector carries those signals generally associated with storage devices and arrays including power control signals, whereas the host connector carries those signals generally associated with the host such as system status signals. The storage connector and the host connector also carry the data being transmitted to and from the storage disks, preferably using a fibre channel interface. 
     These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In order that the manner in which the advantages and objects of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
     FIG. 1 is a schematic block diagram illustrating a representative RAID network in accordance with the present invention; 
     FIG. 2 is a schematic block diagram illustrating one embodiment of a RAID system in accordance with the present invention; 
     FIG. 3 is a schematic block diagram illustrating one embodiment of a RAID system with a modular controller in accordance with the present invention; 
     FIG. 4 is a phantomed top view illustrating one embodiment of a RAID controller card set of the present invention; 
     FIG. 5 is a schematic block diagram illustrating one embodiment of a controller core card of the present invention; 
     FIG. 6 is a schematic block diagram illustrating one embodiment of a host port of the present invention; 
     FIG. 7 is a schematic block diagram illustrating one embodiment of a storage port of the present invention; 
     FIG. 8 is a schematic block diagram illustrating one embodiment of a controller interface card of the present invention; and 
     FIG. 9 is a schematic flowchart diagram illustrating one embodiment of a RAID controller customization method of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a representative RAID network  100  suitable for use with the present invention. The RAID network  100  as shown includes a number of workstations  110  and servers  120  interconnected by a local area network  130 . The servers  120  may be configured to provide specific services such as print services, storage services, Internet access, and the like. 
     In the depicted embodiment, the servers  120  provide storage services to the local area network  130  via one or more storage arrays  140 . The servers  120  are interconnected with the storage arrays  140  through a storage network  150 . In one embodiment, the storage network  150  is a local area network in which the servers  120  and the storage arrays  140  are housed within the same facility or campus. In another embodiment, the storage network  150  is a wide area network with the servers  120  and the storage arrays  140  housed in geographically disparate locations. 
     FIG. 2 shows one example of a RAID system  200  illustrating the need for the present invention. The RAID system  200  includes a storage array  210  and one or more RAID controllers  220 . The RAID system  200  preferably includes a plurality of RAID controllers  220  in order to achieve increased reliability through redundancy. The storage array  210  is also preferably redundant by including a number of storage devices  230 . The storage devices  230  are interconnected with an array loop  240 . The array loop  240  also interconnects the RAID controllers  220  with the storage array  210 . In the depicted embodiment, the array loop  240  is a point-to-point loop such as that defined by the fibre channel standard. 
     In one embodiment, the fibre channel drives are dual ported devices. Thus, both controllers are connected to all of the disk drives and are configured to conduct back-end communications on the same buses on which data transfer occurs. At the host side, a switch device is used to connect the controllers to the hosts. Thus, in this embodiment, a controller to controller connection on the host side is unnecessary, as all communications occur on the storage side where the captive (non shared) bus for the storage system resides. The multi-point connections are preferably present on the host side and are used primarily for fault redundancy.) 
     In the depicted embodiment, the RAID controllers  220  each support a host connection  250 . The RAID controllers  220  receive access requests via the host connection  250  and service those requests by transferring blocks of data to and from the storage array. The blocks of data that are transferred to the storage array are redundantly encoded to permit error detection and data recovery in the event of a failure of a one of the storage devices  230 . 
     In addition to data redundancy, the RAID controllers  220  preferably support some type of failover mechanism. In one embodiment, for example, one of the RAID controllers  220  is a primary controller while the remaining RAID controllers  220  are standby controllers that monitor the activity of the primary controller. One of the standby controllers is activated in the event of a failure of the primary controller. A host loop  260  facilitates the standby controllers servicing access requests in the event of a primary controller failure. In another embodiment, the RAID controllers  220  support load sharing. If a failure occurs in one of the RAID controllers  220 , the remaining RAID controllers  220  pick up additional traffic load via the host loop  260 . 
     In the preferred embodiment, the RAID controllers  220  support data caching via an onboard storage cache. Onboard storage cache improves the performance of the RAID system  200 . In the event of a power failure, unwritten data is flushed from the storage cache to the storage array  210  while the RAID controller  220  operates on backup power. 
     Many different packaging options exist for the RAID controllers  220 . In one embodiment, the RAID controllers  220  are housed in the same chassis as the storage array  210 . In another embodiment, the RAID controllers  220  are contained within the servers  120  shown in FIG.  1 . The form factor of the chassis within which the RAID controllers  220  are housed, and the electrical interface used therein is often manufacturer or product dependent. 
     Various options also exist for providing backup power. In one embodiment, the RAID controllers  220  support an onboard battery backup unit. In another embodiment they interface to a standalone backup power unit. The RAID controllers  220  may include status indicators of various types including controller availability, storage cache status, host connection status, array loop status, and the like. Due to the aforementioned options as well as unanticipated options, and different physical and connectivity constraints, it is preferable that the RAID controller  220  be easily customizable in order to support the desired options and differing parameters at a reasonable cost. 
     FIG. 3 is a schematic block diagram illustrating one embodiment of a RAID system  300  that includes a modular RAID controller  310  that addresses the need for quick, low-cost customization. The RAID system  300  also includes a host  320  and the storage array  210 . The storage array  210  contains the storage devices  230  interconnected by the array loop  240  of FIG.  2 . The modular RAID controller  310  receives access requests from the host  320  via the host connection  250 . 
     The modular RAID controller  310  is, under the present invention, partitioned into the RAID controller core  330  and the RAID controller interface  340 . The RAID controller core  330  contains functions that are essential to a RAID controller and which are most readily subject to standardization. The RAID controller interface  340  contains elements that tend to vary between various RAID controller designs such as I/O connectors, power control including battery backup, status indicators, hot swap features, physical dimensions, and the like. Modularization of the modular RAID controller  310  allows customization to exclusively effect the RAID controller interface  340  without requiring modification to the RAID controller core  330 . 
     FIG. 4 is a phantomed top view depicting one embodiment of a RAID controller card set  400  of the present invention. FIG. 4 illustrates the physical outline of a controller core card  410  and a controller interface card  420 . The controller core card  410  preferably corresponds to the RAID controller core  330  while the controller interface card  420  preferably corresponds to the RAID controller interface  340 . The combination of the two cards  410 ,  420  in the RAID controller card set  400  may, under the present invention, be used to implement the modular RAID controller  310  of FIG.  3 . 
     The controller interface card  420  contains those components that are generally unique to a particular customer or product such as I/O connectors, power control including battery backup, status indicators, hot swap features and the like. The controller interface card  420  also matches the physical constraints, form factor and electrical interface of the particular application. 
     The controller core card  410  contains those components associated with costly development and production such as control processor, storage cache and channel controllers. Overall product cost is minimized by standardizing the controller core card  410  across various different RAID systems and their various form factors, and value added features and options. Inventory costs are minimized and forecasting errors offset by using the modular RAID controller card set  400  for multiple customers and product lines. 
     In the depicted embodiment, the controller core card  410  is a daughter card and may mount exclusively upon the controller interface card  420 . Preferably, the controller interface card  420  is connected and mates with a plurality of connectors associated with communication ports. In the depicted embodiment these include a host port connector  430  and a storage port connector  440 . The host port connector  430  and the storage port connector  440  provide physical and electrical connectivity between the controller core card  410  and the controller interface card  420 . Preferably, all communications to and from the controller core card  410  are relayed through the controller interface card  420 . The controller interface card  420  is shown with a cutout  450  that provides physical access to removable components such as a memory module of the controller core card  410 . While the controller interface card  420  is shown with a particular design, the depicted shape is given only by way of example. It should be readily apparent that the controller interface card  420  may be customized in shape and overall dimensions to each particular application. 
     FIG. 5 is a schematic block diagram illustrating more particularly one embodiment of the controller core card  410  of FIG.  4 . The controller core card  410  is preferably configured to support fault-tolerant systems with data redundancy, active standby and load sharing capabilities. Within the controller core card  410 , a control processor  510  accesses data from a control store  520  via an address bus  522  and a data bus  524 . The control processor  510  also configures various devices and accesses configuration information. In one embodiment, the configuration signals are transmitted from the control processor  510  over the data transfer buses  526  and  528 . 
     A host-side data bus  526  and a storage-side data bus  528  are high performance data buses that facilitate the transfer of blocks of data between a host and a storage array such as the storage array  210 . In one embodiment, a CRC engine  530  executes the actual transfers within the controller core card  410  and provides or checks CRC data depending of the direction of the transfer. 
     A host port  540  and a storage port  550  provide access to a host and a storage array respectively via the controller interface card  420 . A data cache  560  stores and caches data blocks and provides an intermediate transfer point for the CRC engine  530 . The CRC engine  530  accesses the data cache  560  through a data cache bus  562 . 
     FIG. 6 is a schematic block diagram illustrating one embodiment of a configuration of the host port  540 . Within the host port  520 , a host port connector  610  carries a number of signals between the controller core card  410  and the controller interface card  420 . A channel controller  620   a , and a channel controller  620   b  support the transfer of blocks of data between the host-side data bus  526  and a host-side transmission bus  625 . The host-side transmission bus  625  includes host transmit signals  625   a  and  625   b , and host receive signals  625   c  and  625   d . The signals on the host-side transmission bus  625  are carried on the host port connector  610 . 
     The host port connector  610  also preferably carries signals associated with a power bus  630 , and a status and control bus  640 . The status and control bus  640  includes debug and test signals  640   a , channel status signals  640   b , channel loop control signals  640   c , controller status signals  640   d , and cache control signals  640   e . In one embodiment, the particular signals carried by the host port connector  610  include those shown in Table 1. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Host Port Status and Control Signals 
               
             
          
           
               
                 Group 
                 Signal Name 
                 Description 
               
               
                   
               
               
                 Debug And Test 
                 MFG_DIAG 
                 Boot in Diagnostic Mode 
               
               
                   
                 PONRST 
                 Reset Signal 
               
               
                   
                 FORCE_DEBUG 
                 Activate Test Port 
               
               
                   
                 UART_TXD 
                 Test Port Transmit Signal 
               
               
                   
                 UART_RXD 
                 Test Port Receive Signal 
               
               
                 Channel Status 
                 H0_ACTIVE 
                 Host Channel 0 Activity 
               
               
                   
                 H1_ACTIVE 
                 Host Channel 1 Activity 
               
               
                   
                 DEV0_ACTIVE 
                 Storage Channel 0 Activity 
               
               
                   
                 DEV1_ACTIVE 
                 Storage Channel 1 Activity 
               
               
                 Channel Loop 
                 H0_LPEN 
                 Loop 0 Arbitration Control 
               
               
                 Control 
                 H1_LPEN 
                 Loop 1 Arbitration Control 
               
               
                 Controller Status 
                 BBU_FAULT 
                 Backup Power Low 
               
               
                   
                 READY 
                 Controller Successfully Booted 
               
               
                   
                 PRTNRFAIL 
                 Partner Controller Failed 
               
               
                   
                 CDIRTY 
                 Cache Has Unwritten Data 
               
               
                 Cache Control 
                 CONCACHE 
                 Flush Cache And 
               
               
                   
                   
                 Change To Write-thru Mode 
               
               
                   
               
             
          
         
       
     
     The power bus  630  comprises various power signals that are appropriate to power low voltage devices as well as standard TTL voltages. In one embodiment shown in Table 1, the debug and test signals  640   a  include a test port transmit and test port receive signal. The depicted embodiment also includes signals that reset the controller, boot the controller in a diagnostic mode, and activate a test port. 
     In the embodiment of Table 1, the channel status signals  640   b  indicate activity on a pair of host channels and a pair of storage channels. The channel loop control signals  640   c  provide arbitration control for a pair of host channels, such as those carried on the host connection  250  and the host loop  260 . The controller status signals  640   d  include signals that indicate when backup power is low, the controller has successfully booted, the partner controller has failed, and the data cache has unwritten data. The cache control signals  640   e  include a signal that facilitates flushing the data cache and changing to a write-through mode. Those skilled in the art will appreciate that changing to write-through mode decreases the probability of system failures in certain situations, for example when operating on backup power. 
     FIG. 7 is a schematic block diagram illustrating one embodiment of the storage port  550 . The storage port  550  is similar in form to the host port  540  and includes a storage port connector  710 , a channel controller  720   a , and a channel controller  720   b . The channel controllers  720   a  and  720   b  manage transfers between the storage-side data bus  528  and a storage-side transmission bus  725 . 
     The storage-side transmission bus  725  includes storage transmit signals  725   a  and  725   b , as well as storage receive signals  725   c  and  725   d . The signals of the storage-side transmission bus  725  are carried by the storage port connector  710 . The storage port connector  710  also carries the signals associated with a power bus  730 , and a status and control bus  740 . The status and control bus  740  includes power control signals  740   a , power status signals  740   b , channel loop control signals  740   c , controller status signals  740   d , and configuration control signals  740   e . In one embodiment, the particular signals carried by the storage port connector  710  include those shown in Table 2. 
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Storage Port Status and Control Signals 
               
             
          
           
               
                 Group 
                 Signal Name 
                 Description 
               
               
                   
               
               
                 Power Control 
                 IDLE 
                 Turn on Backup Power 
               
               
                   
                 DISCHG 
                 Begin Backup Power 
               
               
                   
                   
                 Reconditioning 
               
               
                   
                 CHARGE 
                 Begin backup Power Recharge 
               
               
                 Power Status 
                 PDN 
                 Switching to Backup Power 
               
               
                   
                 BPON 
                 Backup Power ON 
               
               
                   
                 BP_OFF 
                 Backup Power OFF 
               
               
                   
                 DLBPON 
                 Delayed Version of BPON 
               
               
                 Controller Status 
                 CCACHE 
                 Cache is active 
               
               
                   
                 CARD_ID 
                 Card is Master 
               
               
                 Channel Loop Control 
                 DEV1_LPEN 
                 Loop 1 Arbitration Control 
               
               
                   
                 DEV0_LPEN 
                 Loop 0 Arbitration Control 
               
               
                 Configuration Control 
                 SCL, SCA 
                 Serial Data Bus 
               
               
                   
               
             
          
         
       
     
     The storage port  550  is associated with storage arrays such as the storage array  210 . Power control is essential to maintaining data integrity within storage arrays in the event of power disruptions or outages. In the preferred embodiment, the storage port  550  and the storage port connector  710  support a variety of signals that facilitate intelligent power management. For example, the power bus  730  may include various power signals appropriate to operating in a standby mode such as when backup power sources are nearly depleted. In one embodiment, a standby mode maintains data integrity by causing all the devices on the controller core card  410  to shutdown except for the data cache  560 . 
     The embodiment documented in Table 2 includes a variety of signals for intelligent power management. For example the power control signals  740   a  include signals that activate backup power, begin backup power reconditioning, and begin backup power recharging. The power status signals  740   b  includes signals that indicate when backup power is being activated, backup power is now on, backup power is off, and backup power was recently activated. 
     The embodiment documented in Table 2 also includes the channel loop control signals  740   c , the controller status signals  740   d , and the configuration control signals  740   e . The channel loop control signals  640   c  provide arbitration control for a pair of storage channels, such as those carried on the array loop  240 . The controller status signals  740   d  are status signals that are relevant to a storage array such as a signal for indicating that the data cache is active, and a signal to indicate if the controller is a master controller. The configuration control signals  740   e  enable the control processor  510  to read configuration information from the controller interface card  420 . In the depicted embodiment, the configuration information determines the operating parameters of the RAID system  300  such as the type of data redundancy used when storing data on the storage array  210 . 
     FIG. 8 is a schematic block diagram illustrating one embodiment of the controller interface card  420 . In the depicted embodiment, the controller interface card  420  complements and mates with the controller core card  410  via the host port connector  610  and the storage port connector  710 . The embodiment depicted in FIG. 8 also includes a backplane connector  805 , a power control unit  810 , one or more status indicators  820 , a configuration store  830 , a hot swap controller  840 , one or more external ports  850 , a power bus  630 , a power bus  730 , a control and status bus  640 , a control and status bus  740 , a host-side transmission bus  625 , and a storage-side transmission bus  725 . 
     The backplane connector  805  provides electrical and physical connectivity to other elements of a particular RAID system or application including, for example, alarm devices, system power and system ground. The power control unit  810  receives system power as well as backup power and provides the power signals required by the power bus  630  and the power bus  730 . The power control unit  810  also receives and provides appropriate signals from the status and control bus  640  as well as the status and control bus  740 . Examples of these signals include the power control signals  740   a , the power status signals  740   b  and the controller status signals  640   b.    
     The various signals received and provided by the control unit  810  facilitate intelligent power management by the power control unit  810  and the RAID controller card set  400 . For example the RAID controller card set  400  may operate in a standby mode when system power is unavailable. The standby mode may allow certain critical operations while logging or deferring others. In one embodiment, the standby mode provides power to the data cache  560  while all other components are shut down. 
     The external ports  850  provide external access for the host-side transmission bus  625  and the storage-side transmission bus  725 . For example, in one embodiment the external ports  850  connect to the array loop  240  and the host loop  260 . In one embodiment the external ports  850  are routed through the backplane connector  805 . 
     In the depicted embodiment, the hot swap controller  840  detects whether the controller core card  410  is attached to the controller interface card  420  and fully operational. If not, the hot swap controller  840  bypasses the controller interface card  420  by bridging the signals from two pairs of external ports to one another in place of the host-side transmission bus  625  and the storage-side transmission bus  725 . In one embodiment the hot-swap controller  840  and the power control unit  810  work together to detect insertion or removal of the controller interface card set  400  into a system backplane and properly stage the power signals to prevent malfunctioning or failures within the RAID controller card set  400 . 
     The controller interface card  420  is designed to customize and adapt the RAID controller card set  400  to a particular RAID application or system. Therefore, the precise embodiment of the controller interface card  420  is subject to the requirements of the particular RAID product or system. Some of the elements may be eliminated or minimized according to the desired constraints. For example, some embodiments may include custom components such as a backup battery carried on the controller interface card  420 , while others do not. In practice, the depicted embodiment may be a reference design from which a plurality of controller interface cards  420  are designed and optimized for a particular RAID product or system. Providing a reference design lowers the cost, and hastens the production and deployment of the RAID controller card set  400  and the corresponding modular RAID controller  310 . 
     FIG. 9 is a schematic flowchart diagram illustrating one embodiment of a RAID controller customization method  900  of the present invention. The method  900  of FIG. 9 will be discussed by way of example with reference to the system of FIGS. 1 through 8, but it should readily apparent that the method of FIG. 9 may be conducted independent of the embodiments discussed herein for FIGS. 1 through 8. The customization method  900  starts  905 , after which a controller core card such as the controller core card  330  of FIG. 3 is provided  910 . A controller interface card such the controller interface card  340  of FIG. 3 is then also provided  920 . In practice, a number of controller interface cards may be available for deployment each with particular features. When a selection of controller interface cards are available, the method  900  also includes selecting  922  the controller interface card appropriate for a particular product or application. 
     In one embodiment, the controller interface card  940  is then customized  925 . This may comprise adding components particular to the application, such as a backup battery or extra memory, or the like. Any other customization steps may likewise be conducted. 
     Under the customization method  900  the controller core card  330  is then attached  930  to the controller interface card  340 . In one embodiment, the controller core card  330  is a daughter card, and attaching the controller core card  930  comprises fastening the controller core card  930  in place using fasteners associated with the host port connector  610  and the storage port connector  710 . The custom configured controller card set  310  is then ready for operation  935 , after which the method  900  terminates  940 . 
     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the subsequent description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.