This guide offers instruction on the installation and use of Open Cache Acceleration Software for Linux (Open CAS Linux). It will be helpful for the end user to have a basic knowledge of storage management and Linux* system administration.

Open CAS Linux Overview

Open CAS Linux accelerates Linux applications by caching active (hot) data to a local flash device inside servers. Open CAS Linux implements caching at the server level, using local high-performance flash media as the cache drive media within the application server, thus reducing storage latency.

Open CAS Linux installs into the Linux operating system as a kernel module. The nature of the integration provides a cache solution that is transparent to users, applications and your existing storage infrastructure. No storage migration or application changes are required.

As shown in the figure below, initial read data is retrieved from backend storage and copied to the Open CAS Linux cache. A second read promotes data to system memory. Subsequent reads are returned at high-performance RAM or flash speed. In Write-through mode, all data is written synchronously to both the backend storage and the cache. In Write-back mode, all data is written to the cache then eventually flushed to the backend storage. When the cache is full, newly identified active data evicts stale data from the cache, utilizing the Open CAS Linux proprietary eviction algorithm.

alt text Block Diagram - Write-through and Write-back modes

Open CAS Linux, by default, employs a block-based caching architecture that caches all of the activity on the selected core device.

Documentation Conventions

The following conventions are used in this manual:

code examples, command line entries (may also begin with #)

file content examples

  • Italic - user interface items, filenames, etc.

  • < > - denotes mandatory commands

  • [ ] - denotes optional commands

  • command - highlights or differentiates a command to execute from other text


Refer to the resources and tools listed in the following table for assistance with Open CAS Linux testing and operations, or to learn more about caching and application IO performance management.

Reference Documents

Name Location
DT generic data testing program

Revision History

Revision Number Description Date
01 Initial Release April 2018
02 Updated Information for Write-only Mode September 2019