The CAS flash caching product is fundamentally an automated storage tiering product for use with solid state flash drives (SSD). It allows users to boost IOPS locally for specific applications by identifying active data and promoting it to read cache/memory.
Some storage tiering products can suffer from so-called Monday Morning Syndrome, in which data that was being used heavily is relegated to slower access spinning disk during low-usage periods and then takes time to be moved back to flash when operations re-start, after the weekend for example.
According to Andrew Flint, Intel product manager, the CAS flash cache software product avoids this by applying an “ageing curve” to data in apps specified by the admin.
“The hottest data on Friday would still be hot on Monday,” said Andrew Flint.
He added that CAS users can restrict the product’s I/O boost to specific applications and that I/O from other workloads can’t push data out of cache.
Currently, Intel’s CAS products provide read-only cache, which means they promote existing data from spinning disk HDDs. That means that there are no unique instances of data residing in cache that could be threatened by a server outage.
However, Intel has plans to release a write-cache CAS product later this year. In such a scenario, freshly-written data must be protected because it is unique and its loss could be critical in some use cases, such as financial trading.
This is an inherent issue with server-side flash use where a host outage could result in unique instances of written data being lost. Vendors are working on ways of protecting data between instances of flash cache to get around this, such as Dell’s Project Hermes.
Intel also aims to address this challenge by writing data to multiple instances of flash storage in servers and/or arrays, said Flint.
“We are looking at the ability to do safe write acceleration. There’s always the possibility of system failure when data is written, but we will implement a scenario where writes go to other nodes,” said Flint.
Intel’s CAS can be used with array-based drive-format or server-side PCIe flash storage, creating cache in either format.
The new Linux CAS product can be downloaded for free as a GPL code release or bought as a supported product.