Richard Stanley Ohran

US Patent:

6338126, Jan 8, 2002

Filed:

Dec 6, 1999

Appl. No.:

09/455072

Inventors:

Richard Ohran - Provo UT
Dan Price - Orem UT
Randall Johnson - Pleasant Grove UT

Assignee:

Legato Systems, Inc. - Mountain View CA

International Classification:

G06F 1216

US Classification:

711162, 707204, 709213, 714 6

Abstract:

A primary computer system and a backup computer system each have an associated memory. For each write request, a copy of the request is forwarded to a delay buffer and memory queue associated with the primary computer system, and a copy is forwarded to a memory queue of the backup computer system. The backup computer system transmits an acknowledgement signal to the primary computer system when the backup computer system receives its copy of the request. The write request in the delay buffer of the primary computer system is executed in the primary memory only upon receipt of this acknowledgement signal. Thus, the backup computer system knows of every request executed in the primary memory. The write request is executed in the backup memory at any time after the backup computer system receives the write request. The write requests are deleted from the memory queues (primary and backup) when the associated computer system confirms that the write request was executed in the memory of the opposite computer system.

US Patent:

6397307, May 28, 2002

Filed:

Feb 23, 1999

Appl. No.:

09/255486

Inventors:

Richard S. Ohran - Provo UT

Assignee:

Legato Systems, Inc. - Mountain View CA

International Classification:

G06F 1216

US Classification:

711161, 711162, 707204, 707202, 707203, 380280, 380283

Abstract:

A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel. In addition, update files may be cached by the primary system so that requests for mirrored or archived data may be fulfilled by the primary system cache rather than requiring access to the secondary system.

US Patent:

6526487, Feb 25, 2003

Filed:

Oct 22, 2001

Appl. No.:

10/037117

Inventors:

Richard Ohran - Provo UT
Dan Price - Orem UT
Randall Johnson - Pleasant Grove UT

Assignee:

Legato Systems, Inc. - Mountain View CA

International Classification:

G06F 1216

US Classification:

711162, 707204, 709213, 714 6

Abstract:

Obtaining mirrored data so that the original data can be recovered after failure without transmitting the entire mirrored data between computers. A write request at a primary computer is stored in a delay buffer and a copy is transmitted to a backup computer, where it is stored in a delta queue. The backup computer executes the copy of the write request to the mirrored data and transmits an acknowledgement to the primary computer that the copy of the write request has been received. In response to the acknowledgement, the primary computer executes the write request stored in the delay buffer. The computers send to each other subsequent acknowledgements of the write request execution, enabling the computers to delete the write requests. If the primary computer fails, the primary computer can recover the original data by receiving only the copies of write requests that remain stored in the delta queue.

US Patent:

6560617, May 6, 2003

Filed:

Mar 18, 1999

Appl. No.:

09/271585

Inventors:

John M. Winger - Alpine UT
David Green - Pleasant Grove UT
Richard S. Ohran - Provo UT
Michael R. Ohran - Orem UT

Assignee:

Legato Systems, Inc. - Mountain View CA

International Classification:

G06F 1730

US Classification:

707204, 707 10, 707100, 707200, 714 4, 714 6, 714 15

Abstract:

A method for providing rapid recovery from a network file server failure through the use of a backup computer system. The backup computer system runs a special mass storage access program that communicates with a mass storage emulator program on the network file server, making the disks or other mass storage devices on the backup computer system appear like they were disks on the file server computer. By mirroring data by writing to both the mass storage of the file server and through the mass storage emulator and mass storage access program to the disks on the backup computer, a copy of the data on the file server computer is made. Optionally, selected portions of the data read through the mass storage emulator program can be altered before being returned as the result of the read operation on the file server. In the event of failure of the file server computer, the backup computer can replace the file server, using the copy of the file servers data stored on its disks. A single backup computer can support a plurality of file server computers.

US Patent:

6609183, Aug 19, 2003

Filed:

May 28, 2002

Appl. No.:

10/157427

Inventors:

Richard S. Ohran - Provo UT

Assignee:

Legato Systems, Inc. - Mountain View CA

International Classification:

G06F 1216

US Classification:

711161, 711162, 707202, 707203, 707204

Abstract:

A method and system for mirroring and archiving mass storage. A primary mass storage and a secondary mass storage are synchronized to contain the same data. Thereafter, a primary system tracks changes made to the primary mass storage. These changes are consolidated periodically into update files, the consolidations representing changes made to the primary mass storage during a time interval that ends when the primary mass storage is in a logically consistent state. These update files contain only those changes necessary to represent the modified state of the primary mass storage at the time of the update. The primary system then transfers the update files to a secondary system to bring the secondary mass storage current with the primary mass storage. The consolidation minimizes the amount of information that must be transferred and therefore allows for a relatively low band width communication channel. In addition, update files may be cached by the primary system so that requests for mirrored or archived data may be fulfilled by the primary system cache rather than requiring access to the secondary system.

US Patent:

6871271, Mar 22, 2005

Filed:

Dec 20, 2001

Appl. No.:

10/029189

Inventors:

Richard S. Ohran - Henderson NV, US
Michael R. Ohran - Orem UT, US

Assignee:

EMC Corporation - Hopkinton MA

International Classification:

G06F012/16

US Classification:

711162, 711161, 711167, 714 6, 707204

Abstract:

Restoring a mass storage device, including the corresponding data blocks stored thereon, to a state in which it existed at a prior instant in time to minimize the data loss caused by data blocks becoming corrupt or lost. After a mirrored or backup copy has been made, data blocks that are to be overwritten in response to a write request are stored in a preservation memory prior to being overwritten. The data blocks stored in the preservation memory are time-stamped to designate the chronological order by which the data blocks were overwritten. If data becomes corrupted, the data blocks of the preservation memory are applied to the corrupted data in reverse chronological order until such time that a valid, non-corrupted set of data is obtained. In this manner, data more recent than that associated with the full mirrored or backup copy can be reconstructed.

US Patent:

6931502, Aug 16, 2005

Filed:

Feb 25, 2003

Appl. No.:

10/374694

Inventors:

Richard Ohran - Provo UT, US
Dan Price - Orem UT, US
Randall Johnson - Pleasant Grove UT, US

Assignee:

EMC Corporation - Hopkinton MA

International Classification:

G06F012/16

US Classification:

711162, 714 6

Abstract:

Recovering mirrored data after the failure of a computer using write requests stored in a delta queue of an associated computer without transmitting all of the mirrored data. A write request at a primary computer is stored in a delay buffer. A copy of the write request is transmitted to a backup computer and stored in a delta queue. The backup computer executes the copy of the write request and transmits acknowledgement of the receipt of the write request to the primary computer. In response to the acknowledgement, the primary computer executes the write request stored in the delay buffer. The computers then exchange subsequent acknowledgements of the write request execution, enabling the computers to delete the write requests. If the primary computer fails, the primary computer recovers data by receiving only the copies of write requests that remain stored in the delta queue of the backup computer.

US Patent:

6941490, Sep 6, 2005

Filed:

Nov 29, 2001

Appl. No.:

09/997656

Inventors:

Richard S. Ohran - Henderson NV, US

Assignee:

EMC Corporation - Hopkinton MA

International Classification:

G06F011/00

US Classification:

714 15, 714 5, 714 6

Abstract:

Data blocks lost at a primary mass storage are restored while allowing the primary computer system to access the lost data block before full restoration. Restoration occurs along two channels. In the first channel, read requests issued by the primary computer system are handled by obtaining the requested data block from the backup mass storage device. The retrieved data block is then written to the primary mass storage, thereby restoring the primary mass storage for that data block. In the second channel of restoration, a snapshot copy of a selected data set of the backup mass storage is made and transported to the primary system. If the corresponding data block in the primary mass storage has a current data block, the data block is not written from the snapshot copy to the primary mass storage. Otherwise, the data block is copied from the snapshot copy to the primary mass storage.