Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
2000-09-26
2003-03-18
Mizrahi, Diane D. (Department: 2175)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06535891
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a method and apparatus for identifying accesses to a repository of logical objects (e.g., a file system or database) stored on a data storage system by examining information relating to accesses to physical storage locations in the data storage system.
DESCRIPTION OF THE RELATED ART
Computer systems typically include one or more processing devices, as well as one or more data storage devices.
FIG. 1
is a block diagram of a typical computer system
100
, which includes a host computer
110
, having a processor
120
and a memory
130
, and a storage system
140
. The storage system
140
can include any of a number of different types of storage devices (e.g., tape storage devices, floppy diskette storage devices, disk drive storage devices, etc.), or a combination of a number of different types of storage devices.
Application programs for the host computer
110
typically execute on the processor
120
and operate on logical objects (e.g., files, etc.) that are visible to the application programs, and that each includes one or more logically related blocks of data. The logically related blocks of data forming each logical object are physically stored in the storage system
140
. Thus, as shown in
FIG. 2
, a typical computer system
100
can be viewed as having a number of hierarchical spaces or layers, including an application space
310
, a physical space
330
, and a mapping layer
320
disposed therebetween. As mentioned above, application programs executing on the host computer
110
operate on logical objects (e.g., files) in application space
310
. The data forming the logical objects is stored on one or more storage devices
341
-
343
that are included in the storage system
140
and define the physical space
330
. Thus, the data stored in the storage device
140
typically is organized in units of storage termed “physical blocks” that each includes a number of bytes of data (e.g., 512 bytes). Conversely, the logical objects operated upon in application space
310
are made up of “logical blocks”. The mapping layer
320
typically is a data structure that maps the logical objects in application space
310
into physical space
330
. Although the size of a logical block of data may correspond one-to-one to that of a physical block stored in physical space
330
, this is not necessarily the case. Rather, one logical block of data can map to two or more physical blocks of data, or alternatively, multiple logical blocks of data can map to a single physical block of data in physical space
330
.
The storage system
140
presents logical volumes of storage to the host computer
100
. These logical volumes of storage can each correspond to one of the physical storage devices
341
-
343
included within the storage system
140
. However, when the storage system
140
is an intelligent storage system, it may include a layer of mapping, within the physical space
330
, between the logical volumes presented to the host computer
100
and the actual physical storage devices
341
-
343
. Thus, there need not be a one-to-one correspondence between the logical volumes presented to the host computer
110
and the physical storage devices, as a single logical volume can be spread across multiple physical storage devices, or alternatively, a number of physical storage devices can be combined to store the data for a single logical volume.
The mapping layer
320
maps each logical object specified in application space
310
to one or more unique locations (e.g., physical blocks) in physical space
330
where the data forming the logical object is stored. The mapping layer
320
can include a single layer of mapping, such as a file system
322
or a Logical Volume Manager (LVM)
324
, or as shown in
FIG. 2
, can include multiple mapping layers
322
and
324
. LVMs typically are used in larger computer systems having a number of storage devices, and enable volumes of data storage to be managed at a logical (rather than physical) level. The presence or absence of the LVM
324
is transparent to both the application space
310
and the file system
322
. In this respect, the file system simply maps from the application space
310
to what the file system perceives to be the physical space
330
. If another layer of mapping, such as an LVM, is included in the mapping layer
320
, it simply means that the result of the mapping done in the file system does not indicate the final mapping to the physical space
330
.
In a typical computer system, the storage system
140
has no understanding of the logical relationship between the blocks of data that it stores in physical space
330
. This is true because the logical grouping of data is done in the application and mapping spaces
310
,
320
, and is not passed to the storage system
140
. Similarly, in a typical computer system, an application program executing in application space
310
has no understanding of where the data that forms a particular logical object is stored in physical space
330
.
In many computer systems, sets of logical objects (e.g, files) are organized at a higher logical level, such that the computer system includes one or more repositories of logical objects. Examples of such repositories include a file system and a database, although other repositories of logical objects are also possible. Such repositories are to be distinguished from a single logical object, which may be made up of multiple logical blocks of storage, but which comprises only a single logical object that is visible to application programs executing in application space.
SUMMARY OF THE INVENTION
One illustrative embodiment of the invention is directed to a method for use in a computer system, the computer system including a host computer having an application space and defining a repository of logical objects visible to the application space, the computer system further including a storage system that a defines a physical space wherein data representing the repository of logical objects is stored, the repository of logical objects including a plurality of logical objects. The method comprises acts of: (A) mapping the repository of logical objects from the application space to the physical space to create mapping information identifying which units of storage in the physical space store the repository of logical objects; and (B) making the mapping information visible to the application space.
A further illustrative embodiment of the invention is directed to a computer readable medium encoded with a program for execution on a computer system including a host computer and a storage system, the host computer having an application space and defining a repository of logical objects visible to the application space, the storage system defining a physical space wherein data representing the repository of logical objects is stored, the repository of logical objects including a plurality of logical objects. The program, when executed on the computer system, performs a method comprising acts of: (A) mapping the repository of logical objects from the application space to the physical space to create mapping information identifying which units of storage in the physical space store the repository of logical objects; and (B) making the mapping information visible to the application space.
Another illustrative embodiment of the invention is directed to a method for use in a computer system, the computer system including a host computer and a storage system, the host computer having an application space and defining a repository of logical objects visible to the application space, the repository of logical objects including a plurality of logical objects. The method comprises acts of: (A) executing an operation on the repository of logical objects; and (B) subsequent to the act (A), executing an incremental operation on the repository of logical objects, such that the incremental operation is performed only on those of the plurality of logical objects that have changed subsequent to the execution of the op
Blumenau Steven M.
Fisher Michel
EMC Corporation
Mizrahi Diane D.
Wolf Greenfield & Sacks P.C.
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