Method and program product for managing data access routes in a data storage system providing multiple access routes

#This invention relates to data storage systems used with computers and computer networks. In particular, the invention relates to a method and program product for managing and switching data access routes to a data storage arrangement such as a disk array.

#File systems and disk arrays utilize two different methods for accessing data stored on a data storage medium. The two methods are distinguished by a number of characteristics. In a file system for example, files are accessed using a file abstraction. That is, data is represented by a file which may be opened, closed, created, deleted, read, and written. Data is managed in a file system through a hierarchy of files and directories. This hierarchical data management is commonly seen as a significant advantage over other data management schemes. File systems also support both data sharing and data storage device sharing. Security within data storage devices is based on file and directory level access control lists standardized as part of the file system protocols. Another advantage of file systems is that client/server compatibility is based on a small number of well-supported protocols. However, file system performance is reduced by data storage disk-resident file mapping arrangements which are required to map data for a file to physical or virtual locations of the storage media associated with a data storage device.

#A disk array is a storage system that employs a number of separate storage devices or disks and manages data across all of the separate devices. These disk array storage systems are popular for implementing data storage redundancy schemes to guard against individual storage device failures. In contrast to a file system, data is accessed in a disk array using a block storage abstraction. That is, data is mapped to large contiguous storage spaces or logical units and is accessed as blocks contained in these logical units. Each block in a logical unit represents a certain amount of data storage space, commonly 512 bytes of storage space. The stored data in a disk array is managed as physical and virtual data storage devices represented by volumes and/or logical units. Although the block storage abstraction may improve the speed at which large amounts of data may be written and retrieved from the storage devices, there are a number of drawbacks associated with disk arrays as compared to file systems. One drawback is that client/server compatibility for disk arrays is subject to a variety of constraints that vary across clients and servers. Also, disk arrays support only device sharing but not data sharing. Furthermore, security within devices is based on vendor unique features.

#FIG. 1 is a diagrammatic representation of a data storage system providing alternate data access routes which may be managed according to the present invention.

#FIG. 2 is a diagrammatic representation showing groupings of various software processes which operate in the data storage system shown in FIG. 1.

#FIG. 3 is a diagrammatic representation showing the interactions between the various software processes shown in FIG. 2.

#FIGS. 1 through 7 are referenced here to describe the structure and operation of a data storage system 100 that provides multiple data access routes. This example data storage system 100 utilizes block access storage devices 103 to actually store data, but maintains file abstractions for the stored data or data sets, and thus retains the important benefits associated with file systems. Data storage system 100 provides two alternative access routes for stored data sets or files, a file system access route and a direct block access route. File system operation access requests that invoke the direct block access route may be referred to as “divertible operations,” whereas file system operation access requests that invoke the file system access route may be referred to as “non divertible operations.” The dual access routes in data storage system 100 may be managed according to methods embodying the principles of the present invention. This route management process will be described with reference to FIGS. 8 through 11.

#The following disclosure will refer for convenience to the particular data storage system 100 illustrated through FIGS. 1 through 7. Thus, the access route management method according to the invention will be described with reference to two alternate data access routes and specifically to a file system access route and a direct block access route. Also, the data sets stored in the system will be referred to as “files.” However, it should be borne in mind that the invention is not limited to use with the specific data storage system 100 shown in the figures or to data storage systems that maintain file abstractions. The invention is also not limited to data storage systems which provide only two different access routes.

#Referring to FIG. 1, data storage system 100 includes a data processing arrangement 101 and an array 102 of separate storage devices 103. In the form of the invention shown in FIG. 1, data processing arrangement 101 includes two separate processors, an array controller processor 105 and a file system processor 106. A system bus 104 interconnects the two processors 105 and 106, a storage device adapter 107, and an input/output port 108. The separate adapter 107 shown in FIG. 1 provides an interface to the storage device bus 109. Also, a hardware protocol stack 110 is associated with the input/output port 108 for providing network communication services which allow system 100 to communicate with a computer network 111. Computer network 111 includes one or more file system clients 112 that have file system access to data storage system 100. These file system clients 112 represent separate computing devices such as personal computers or workstations on network 111.