Abstract: A system and method for controlling the creation of stable disk images. Data is transmitted to an application program interface identifying the storage object. The application program interface returns a list with one or more methods appropriate for quiescing or for freezing the storage object.

Abstract: A system and method of characterizing a logical storage object. Information associated with the logical storage object is stored. The information includes information characterizing quiesce capabilities and split characteristics for the logical storage object. That information is transmitted to a processor and is used to characterize the logical storage object.

Abstract: Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.

Abstract: A method, system, computer system, and computer-readable medium for maintaining up-to-date, consistent copies of primary data without the need to replicate modified data when the data were modified as a result of an operation that is not an application-driven write operation captured during replication. Selected storage management operations are performed on the primary and secondary data stores at points in time when the data are the same to ensure that the data stored within the data stores remain consistent. These selected storage management operations include operations that produce modified data stored in the primary data store, where a portion of the modified data are not replicated to a secondary node. Other types of storage management operations are selected to be performed on both the primary and secondary data stores, where the operations do not directly change data in the primary data store, but may affect data stored in the primary data store.

Abstract: Disclosed is a method and apparatus for restoring a corrupted data volume. In one embodiment, the method includes creating a backup copy of the data volume before the data volume is corrupted. Data transactions that modify the contents of the data volume are stored in a transaction log. After detection of the data corruption, a virtual copy of the backup copy is created. Thereafter, select data transactions stored in the transaction log, are applied to the virtual copy. Data of the corrupted data volume is then overwritten with data of the backup copy and data of the virtual copy after applying data transactions to the virtual copy.

Abstract: In a process to restore a data volume in a first memory, a virtual point-in-time (PIT) copy of the data volume is created. Creating the virtual PIT copy includes creating first, second and third maps in memory. Each of the first, second, and third maps includes a plurality of multi-bit entries. Each of the entries of the first and second maps corresponds to a respective memory region of the first memory, while each of the entries of the third map corresponds to a respective memory region of a second memory for storing data of the virtual PIT copy.

Abstract: A system and method for an election and data majority mechanism that solves problems such as bit flipping, mistracking, miscaching, and I/O status errors during real-time operations. Multiple copies of data are stored on various storage media of a data processing system. Errors that occur on the storage media or on other components of the data processing system are resolved by selecting the data with the highest frequency as the data majority. The data majority is propagated throughout the storage media to correct errors.

Abstract: Disclosed is a method and apparatus for tracking in-progress writes to a data volume and a copy thereof using a multi-column bit map. The method can be implemented in a computer system and, in one embodiment, includes creating a data volume in a first memory, and creating a copy of the data volume in a second memory. In response to the computer system receiving a request to write first data to the data volume, the computer system switches the state of first and second bits of a map entry in a memory device, wherein the state of the first and second bits are switched using a single write access to the memory device.

Abstract: A method and system are provided for emulating operating system metadata to provide cross-platform access to storage volumes. The method may include generating operating system metadata for a storage device, wherein the operating system metadata emulates a storage volume hosted under a first operating system. The method may further include making the operating system metadata available to a host computer system, wherein the host computer system runs the first operating system. The operating system metadata enables the host computer system to recognize the storage device as the storage volume hosted under the first operating system.

Abstract: Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.

Abstract: A system and method of identifying methods of quiescing a storage object. Data is received identifying the storage object and a freeze list is generated. The freeze list includes one or more freeze methods appropriate for quiescing the storage object. Generating includes creating a hierarchy of logical storage objects below the identified storage object, associating quiesce characteristics with each logical storage object below the identified storage object and generating freeze vectors as a function of quiesce characteristics associated with each logical storage object below the identified storage object.

Abstract: A system and method of identifying methods of quiescing a storage object. Data is received identifying the storage object and a freeze list is generated. The freeze list includes one or more freeze methods appropriate for quiescing the storage object. Generating includes creating a hierarchy of logical storage objects below the identified storage object, associating quiesce characteristics with each logical storage object below the identified storage object and generating freeze vectors as a function of quiesce characteristics associated with each logical storage object below the identified storage object.

Abstract: Systems, methods, apparatus and software can make use separated I/O processors and strategy processors in performing virtual device I/O operations. I/O processors operating on cluster nodes, storage appliance ports, or other devices can receive I/O operation requests directed to virtual devices, e.g., volumes or virtual logical units. Information about the request is forwarded to a strategy processor, operating independently or as part of larger volume management software where corresponding physical device I/O operations are determined. The physical device I/O operations are sent back to the I/O processor which executes the operations and/or passes the operation on to the appropriate storage device.

Abstract: Disclosed is a method for creating a virtual copy of data stored in a first memory. The virtual copy of data stored in the first memory is created in a second memory in response to a request to create a copy of all data stored in the first memory. Creating the virtual copy includes, in one embodiment, creating first and second tables in memory each one of which comprises a plurality of multibit entries. Each entry of the first table corresponds to a respective memory region of the first memory. Each entry of the second table corresponds to a respective memory region of the second memory. Each first bit of the first table indicates whether the corresponding memory region of the first memory contains valid data. Each second bit of the first table indicates whether data in the corresponding memory region of the first memory has been modified since the first table was created.

Abstract: A virtual copy of data stored in a first memory is created in a second memory. Creating the virtual copy includes, in one embodiment, creating first and second tables in memory each one of which comprises a plurality of multibit entries. Each entry of the first table corresponds to a respective memory region of the first memory. Each entry of the second table corresponds to a respective memory region of the second memory. The first bit of the first and second tables indicates whether the corresponding memory region of the first and second memories, respectively, contains valid data. The second bit of the first and second tables indicates whether data in the corresponding memory region of the first and second memories, respectively, has been modified since the creation of the first and second tables, respectively.

Abstract: Systems and methods for I/O fencing in a shared storage environment are provided. Prior to initiating an I/O request, when feasible, the current time from a local timer is compared to the current state of an interval obtained for the target device. As a result, a device reset occurring while the interval is viable does not arbitrarily end a multiphase I/O operation. However, a device reset occurring once the lease has expired results in a delay or termination of the multiphase I/O operation. As a result, multiphase I/O operations from initiating hosts that have lost contact with the shared storage environment are not allowed to corrupt the shared storage devices.

Abstract: Disclosed is a method and apparatus for refreshing a copy of a data volume. In one embodiment of the method first and second data portions of a data volume are copied to first and second memory blocks, respectively, of a memory coupled to a computer system. First and second bits of a first map stored in memory are then set, wherein the first and second bits correspond to the first and second memory blocks, respectively. The first data portion of the data volume is modified after the first data portion is copied to the first memory block. A first bit in a second map stored in memory is set after data of the first data portion is modified. An instruction is generated to refresh the data contents of the first and second memory blocks. The first bit of the first map is cleared in response to generation of the refresh instruction.

Abstract: A system and method of characterizing a logical storage object. Information associated with the logical storage object is stored. The information includes information characterizing quiesce capabilities and split characteristics for the logical storage object. That information is transmitted to a processor and is used to characterize the logical storage object.

Abstract: A system and method for controlling the creation of stable disk images. Data is transmitted to an application program interface identifying the storage object. The application program interface returns a list with one or more methods appropriate for quiescing or for freezing the storage object.

Abstract: A system and method of identifying methods of quiescing a storage object. Data is received identifying the storage object and a freeze list is generated. The freeze list includes one or more freeze methods appropriate for quiescing the storage object. Generating includes creating a hierarchy of logical storage objects below the identified storage object, associating quiesce characteristics with each logical storage object below the identified storage object and generating freeze vectors as a function of quiesce characteristics associated with each logical storage object below the identified storage object.