Srikumar S Subramanian

7778960, Aug 17, 2010

Oct 20, 2006

11/551303

Paresh Chatterjee - Fremont CA, US
Anandh Mahalingam - Fremont CA, US
Narayanan Balakrishnan - Milpitas CA, US
Srikumar Subramanian - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 17/30

707609, 707802

A method, system, apparatus, and computer-readable medium are described for the background movement of data between nodes in a storage cluster. According to one method, exception tables are generated that include data identifying the areas on each node that need to be migrated to another node and the areas on each node that are to be migrated from another node. The exception tables may be generated in response to the failure of a node in the storage cluster or in other circumstances. A background resynchronization thread utilizes the contents of the exception tables to migrate data between the nodes of the cluster, thereby synchronizing the data stored on the nodes. Input/output operations directed to an area that is to be migrated from another node are redirected to the other node. The methods, systems, apparatus, and computer-readable medium may be utilized with operations including the rebuilding, expansion, contraction, and compaction of a storage cluster.

7987156, Jul 26, 2011

Mar 5, 2008

12/042715

Paresh Chatterjee - Fremont CA, US
Srikumar Subramanian - Fremont CA, US
Ajit Narayanan - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 7/00

707638, 707639, 707649, 711161, 711162

A method, system, apparatus, and computer-readable medium are provided for taking snapshots of a storage volume. According to aspects of one method, each snapshot is represented as a unique sequence number. Every fresh write access to a volume in a new snapshot lifetime is allocated a new section in the disk, called a provision, which is labeled with the sequence number. Read-modify-write operations are performed on a sub-provision level at the granularity of a chunk. Because each provision contains chunks with valid data and chunks with invalid data, a bitmap is utilized to identify the valid and invalid chunks with each provision. Provisions corresponding to different snapshots are arranged in a linked list. Branches from the linked list can be created for storing writable snapshots. Provisions may also be deleted and rolled back by manipulating the contents of the linked lists.

7373366, May 13, 2008

Oct 20, 2005

11/255146

Paresh Chatterjee - Fremont CA, US
Srikumar Subramanian - Fremont CA, US
Ajit Narayanan - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 12/00
G06F 17/30

707204

A method, system, apparatus, and computer-readable medium are provided for taking snapshots of a storage volume. According to aspects of one method, each snapshot is represented as a unique sequence number. Every fresh write access to a volume in a new snapshot lifetime is allocated a new section in the disk, called a provision, which is labeled with the sequence number. Read-modify-write operations are performed on a sub-provision level at the granularity of a chunk. Because each provision contains chunks with valid data and chunks with invalid data, a bitmap is utilized to identify the valid and invalid chunks with each provision. Provisions corresponding to different snapshots are arranged in a linked list. Branches from the linked list can be created for storing writable snapshots. Provisions may also be deleted and rolled back by manipulating the contents of the linked lists.

8010485, Aug 30, 2011

Aug 16, 2010

12/857050

Paresh Chatterjee - Fremont CA, US
Anandh Mahalingam - Fremont CA, US
Narayanan Balakrishnan - Chennai, IN
Srikumar Subramanian - Newark CA, US

American Megatrends, Inc. - Norcross GA

G06F 17/30

707609, 707802

A method, system, apparatus, and computer-readable medium are described for the background movement of data between nodes in a storage cluster. According to one method, exception tables are generated that include data identifying the areas on each node that need to be migrated to another node and the areas on each node that are to be migrated from another node. The exception tables may be generated in response to the failure of a node in the storage cluster or in other circumstances. A background resynchronization thread utilizes the contents of the exception tables to migrate data between the nodes of the cluster, thereby synchronizing the data stored on the nodes. Input/output operations directed to an area that is to be migrated from another node are redirected to the other node in accordance with a timeout period associated with the input/output operations.

8010829, Aug 30, 2011

Oct 20, 2006

11/551311

Paresh Chatterjee - Fremont CA, US
Ajit Narayanan - Fremont CA, US
Anandh Mahalingam - Fremont CA, US
Srikumar Subramanian - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 11/00

714 411, 714 623

A method, system, apparatus, and computer-readable medium are described for providing distributed hot-spare storage in a redundant storage cluster. According to one method, a portion of the unutilized space on the storage cluster is utilized as a distributed hot-spare storage node. Through this mechanism, a redundant storage cluster with N storage nodes may be contracted to a redundant array with N−1 nodes. Thin provisioning and intelligent data placement may also be utilized to implement the distributed hot-spare storage node. Through repeated application of such methods and systems, the failure of any storage node or the sequential failure of multiple storage nodes within a redundant storage cluster results in the recreation of the cluster as a redundant storage array with one fewer node, but with the same redundancy.

8055938, Nov 8, 2011

Jun 9, 2006

11/450653

Paresh Chatterjee - Fremont CA, US
Srikumar Subramanian - Fremont CA, US
Suresh Grandhi - Fremont CA, US
Srinivasa Rao Vempati - Milford MA, US

American Megatrends, Inc. - Norcross GA

G06F 11/00

714 624, 714 621

A method, system, apparatus, and computer-readable medium are provided for storing data at a virtual tape library (“VTL”) computer or server. According to one method, a VTL computer maintains one or more storage volumes for use by initiators on an array of mass storage devices. Space on each of the volumes is allocated using thin provisioning. The VTL computer may also include a cache memory that is at least the size of a full stripe of the array. Write requests received at the VTL computer are stored in the cache memory until a full stripe of data has been received. Once a full stripe of data has been received, the full stripe of data is written to the array at once. The array utilized by the VTL computer may include a hot spare mass storage device. When a failed mass storage device is identified, only the portions of the failed device that have been previously written are rebuilt onto the hot spare. The array may be maintained using RAID-.

8065442, Nov 22, 2011

Nov 19, 2008

12/273996

Paresh Chatterjee - Fremont CA, US
Srikumar Subramanian - Fremont CA, US
Jomy Maliakal - Newark CA, US
Suresh Grandhi - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 7/00
G06F 3/00

710 5, 710 52, 707682, 707648, 707 8, 707201

Technologies are described herein for high-performance and space efficient journaling mechanisms. A journal queue can buffer incoming I/O operations. The queue can be read by a journal write module. The journal write module can form metadata headers to store into the journal along with each I/O operation. Compound metadata headers may be formed for multiple I/O operations and the combination of multiple I/O operations may be efficiently stored to the journal as one journal write. Multiple journal entries may be written into the journal in parallel while maintaining the sequential ordering of the journal. A queue depth threshold can be established for determining if journal entries should be combined into compound entries or not. Multiple concurrent readers can support continuous data protection, and various data replication features. Each reader can be represented as a reader pointer and a journal writer can invalidate reader pointers when related data is overwritten.

8108580, Jan 31, 2012

Apr 16, 2008

12/104129

Paresh Chatterjee - Fremont CA, US
Loganathan Ranganathan - Fremont CA, US
Narayanan Balakrishnan - Milpitas CA, US
Srikumar Subramanian - Fremont CA, US

American Megatrends, Inc. - Norcross GA

G06F 13/12
G06F 13/00

710 74, 711114

Technologies for efficient synchronous replication across heterogeneous storage nodes can provide the performance of high-speed storage units while leveraging low-cost and high-capacity backup storage units within the same system. The performance of low-cost, high-capacity hard disks may be improved by initially storing data into sequential physical locations. A sequential journal of I/Os may be used in a replicated secondary node to allow for rapid completion of I/Os. A separate background process can later scatter the sequentially logged I/O data into its proper location for storage. A programmable n-way router can be configured to route I/Os as needed to improve overall performance of the storage unit. A secondary node log device can also be used to provide continuous data protection (CDP). Lastly, packetizing together I/Os prior to delivery to a secondary node may reduce interrupts and context switches in the primary node, thereby improving performance of the storage system.