Seagate Technology Incorporated

Dot Hill Systems Corporation

Ritvik Viswanatha

Michael David Barrell

Adithya Uligere Narasimhamurthy

Kishan Gelli

Joseph Skazinski

Systems and processes are disclosed to preserve data integrity during a storage controller failure. In some examples, a storage controller of an active-active controller configuration can back-up data and corresponding cache elements to allow a surviving controller to construct a correct state of a failed controller's write cache. To accomplish this, the systems and processes can implement a relative time stamp for the cache elements that allow the backed-up data to be merged on a block-by-block basis.

Preserving data integrity during controller failures

A system includes first and second redundant controllers, and at least one logical volume accessible to the first and second redundant controllers. The system also includes metadata fields associated with the at least one logical volume. The metadata fields include a first age field configured to store a first age value associated with the first controller and a second age field configured to store a second age value associated with the second controller. The first age value and the second age value are employed to provide an indication of whether cache data for the at least one logical volume is valid. The system further includes a processor configured to update the first and second age values in the respective first and second age fields.

Storage controller cache integrity management

Preserving data integrity during controller failure

A storage controller is provided. The storage controller includes a memory storing an indication of a current owner, a previous owner, and a preferred owner for each of one or more logical volumes. The storage controller is configured to write protect the logical volumes where the current owner and the preferred owner is the storage controller and the previous owner of the logical volumes was a different storage controller. For the logical volumes where the storage controller is the preferred but not the current owner, the storage controller is set as the current and preferred owner of the logical volumes that the different storage controller was the current but not the preferred owner for, storage controller is set as the previous owner of the logical volumes that the storage controller is the current and preferred owner of, and allowing read and write access to the one or more logical volumes.

Storage controller cache synchronization method and apparatus

A method for a pair of redundant storage controllers to ensure reliable cached write data transfers to storage device logical volumes is provided. The method includes maintaining metadata including a first number identifying which controller currently owns the volume, a second number identifying which controller previously owned the volume, a third number identifying which controller is a preferred owner of the volume, and an indication if the volume is write protected. The method also includes determining if all volumes currently owned by the controller are write protected. If all volumes currently owned by the controller are write protected, then the method includes verifying that the second controller is working and transferring cache data from the second controller to the first controller. If all volumes currently owned by the first controller are not write protected, then the method includes updating the second number and placing all volumes online.

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Longmont, CO, United States of America

Ritvik Viswanatha