Nimble Storage’s Cache-Accelerated Sequential Layout (CASL) is the foundation for its high performance, capacity efficiency, integrated data protection, and simplified lifecycle management of its storage systems. CASL accelerates applications by using flash as a read cache coupled with a write-optimized data layout. The CASL architecture includes features such as flash-based dynamic cache, which accelerates read access to application data by holding a copy of “hot” active data in flash, and a write-optimized data layout, in which data written by a host is first coalesced, then written sequentially as a full stripe to a pool or disk. Other features of CASL include efficient integrated replication, inline universal compression, instantaneous point-in-time snapshots, and zero-copy clones.
Architectures that use a write cache to accelerate writes are often confused with the CASL architecture, which accelerates write performance using a sequential layout. Though both of these may have some similarities at first glance, many people miss the key elements that differentiate CASL from other architectures on the market.
The purpose of CASL is to accelerate back-end disks by turning random IO into sequential IO. Nimble’s CASL architecture has no predetermined mapping of logical block addresses (LBA) to physical locations or block boundaries with CASL’s support for variable block sizes. CASL does not rearrange blocks; it simply constructs a large set of blocks into a large physical stripe, reducing all random write operations into one. Unlike traditional storage architectures, Nimble’s CASL write performance is not limited by disks and write caches but by the CPUs compressing and decompressing data.
Traditional storage architectures use LBAs, which uses a map of predetermined physical locations on a disk. Data is written to disks as quickly as possible, but random, non-sequential writes have increased latency over sequential writes resulting in larger write latency. Combined with the need to read data from the same disk drives, read performance is decreased more as a disk tries to balance finding requested data and writing incoming data.
Nimble Storage is revolutionizing data storage with the CASL architecture by leveraging the unique properties of flash and disk to deliver high performance and capacity with the only flash optimized solution.