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Method for preserving flash metadata when raid canisters are missing or disabled

IP.com Disclosure Number: IPCOM000236166D
Publication Date: 2014-Apr-10
Document File: 2 page(s) / 81K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a design for a metadata storage architecture in which a battery module detects a power-loss event and then notifies devices that power has been lost. Upon receiving the power-loss notification, the flash controller performs a shutdown sequence, stores metadata, and powers off, ensuring that the metadata is stored in the event of a power loss.

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Method for preserving flash metadata when raid canisters are missing or disabled

Flash controllers have metadata that must be stored on power-loss or shutdown. Typically, flashcards have a source of backup power such as batteries or super-caps that provide enough power in order to store the metadata. The flashcard must be notified or be able to detect a power-loss event and then store the metadata before running out of back-up power. If a flashcard does not have on-board redundant power and the control links for notification of a power-loss event are disabled, then metadata is not stored.

In the novel storage architecture, a battery module detects power loss and then notifies devices that power has been lost. Under the normal power-loss scenario, this power-loss notification packet passes from the battery module Power Control Board, through removable Redundant Array of Independent Disk (RAID) canisters (RAID/XBAR Controller) to the flash devices (Gateway). The gateway signals a power-loss event to the flash controller and stores metadata. To protect against data loss in the scenario where the power-loss message cannot be sent through the path described above, the gateway controller of the flash device signals a power-loss event to the flash controller if both redundant links from the Gateway to the RAID/RAID Controller are in an off-line state for more than 30 seconds. Upon receiving the power-loss notification, the flash controller performs a shutdown sequence,...