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Apparatus and Device for Host Read all the time

IP.com Disclosure Number: IPCOM000232353D
Publication Date: 2013-Nov-03
Document File: 3 page(s) / 102K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is an improved data management method for Solid State Drives (SSD) that allows the host to obtain immediate access to data on external storage.

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Apparatus and Device for Host Read all the time

Systems administrators are installing Solid State Drives (SSD) on open servers for quick access to frequently used data. The servers contain cache management software to cache data for immediate access. This data can also be written to external disk storage. This creates additional cost and data management issues for organizations with the purchase and management of SSD devices as well as administrative activities to ensure the data is copied to external storage to keep data synchronized.

Storage controllers are introducing a way for tiered storage to be extended from the storage controller to a host server. The host server contains software that allows it to serve as an SSD tier of a multi-tier storage system.

This new feature uses statistics from both the host server and the storage controller to decide which volume data can be contained within the host server for faster reads. This solution requires the movement of data to download the statistics from the server to the controller. Once the controller analyzes the statistics, it determines if data should be sent to the host server for immediate access. This creates additional steps, beyond what customers are currently doing, to ensure fast read access of data at the host level.

With this algorithm, read data can be cached on the host server and access to the underlying storage can be bypassed until such a time as the data becomes cold or a write to storage occurs. However, in order to protect against accessing stale read data, the design requires polling for changes in the underlying storage and accessing storage when a change is detected. This overhead to allow the data to be read from the host server itself is not as optimal as desired.

In current art, a host subscribes the volumes to which data will be cached on the internal SSD devices. Once the device is subscribed, storage system receives the read statistics from the host and uses associated internal statistics to determine when the device can perform caching on the internal SSD.

The novel contribution is a method to allow the host to obtain immediate access, as with local SSD, to data on external storage. With this method, a modification of the subscription of a volume indicates to the storage controller that the volume wants immediate read access to volume data. The modification allows a host to perform an immediate read for a volume data whenever the storage system receives a write from same host or another host to update or modify the device data. Although the device

associated with the host is being referred to as the read-only device, it is not limited to reads but can also write data.

Whenever one or more hosts perform a write command to the volumes assigned to the read-only device, the storage controller sends the updated data to the read-only device. The read-only device decides what to do with the updated data. If the read-only host decides to modify any of the vol...