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Method to Improve the Write Response Time in Thin-Provisioning and Snapshot for Flash Storage Systems

IP.com Disclosure Number: IPCOM000241760D
Publication Date: 2015-May-28
Document File: 3 page(s) / 149K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to reduce response time of the writes in thin-provisioning and snapshot for flash storage systems. Based on the provisional write on the write cache of the Redundant Array of Independent Disks (RAID) controller, the method allows the write to proceed before the extent is allocated.

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Method to Improve the Write Response Time in Thin-Provisioning and Snapshot for Flash Storage Systems

In a flash storage system, thin-provisioning is handled by only provisioning the extent storage upon the first write on the extent. Similarly, on snapshot, when a partial extent write happens on an extent shared by more than one volume, a new extent has to be allocated and populated with the original data before the first write can proceed. Both extent allocation and copying data from the shared extent take time. The time spent on preparing the extent directly reflects on the response time of the writes.

To reduce the response time, some systems use sub-extent metadata to track the state of the data at the sub-extent level, to allow the update from the writes and the copy of extent data to go in parallel. However, the response time is still impacted because the writes still need to wait for the extent to be allocated.

The novel method, based on the provisional write on the write cache of the Redundant Array of Independent Disks (RAID) controller, allows the write to proceed before the extent is allocated. Both the tasks of extent allocation and copying of extent data become the background processes and do not impact the response time of the writes.

As the speed of flash storage becomes faster, the trend is for a flash storage system to provide the write cache at the RAID controller in order to reduce the code path length and, hence, improve the response time.

Also in the flash system with inline de-duplication, this invention can reduce the response time as well as prevent the

writes of duplicated data to improve the flash wear situation.

The method uses the write cache in the RAID controller to improve the response time of writes...