Easy Tier® Server, an enhancement to the Easy Tier family, is a unified storage caching and tiering solution. The Easy Tier Server utility enables the caching of storage-system data in multiple hosts. It provides cooperative caching that is based on statistics gathered in both the host and storage system.
Easy Tier Server copies the most frequently accessed, or hottest, data to direct-attached storage (DAS) flash drives (also known as solid-state drives or SSDs) within Easy Tier Server-enabled hosts. Easy Tier Server caching coherency algorithms ensure that the most valuable data is available on the host local flash-drive devices and ensures data integrity across DS8870 internal tiers and hosts’ DAS cache. Data can be read directly from flash memory attached to the host cache rather than from disk drives in the DS8870 storage system. This data-retrieval optimization results in improved performance, with I/O requests that are generally satisfied in microseconds.
- The Easy Tier Server
coherency server, which runs on the DS8870 system.
The Easy Tier Server coherency server manages how data is placed on the SAN storage tiers and the SAN caches. The coherency server asynchronously communicates with the host system (the coherency client) and generates caching advice for each coherency client, based on Easy Tier placement and statistics.
- The Easy Tier Server
coherency client, which runs on the host system.
The Easy Tier Server coherency client maintains local caches on a DAS flash-drive. The coherency client works independently to cache the I/O streams of its applications, providing a real-time performance enhancement. The coherency client uses the Easy Tier Server protocol to establish system-aware caching that interfaces with the coherency server.
- The coherency client issues SCSI commands to a volume to asynchronously communicate with the coherency server.
- The coherency server generates frequency-based advice based on a unified view of the SAN storage, hosts, and their access patterns.
- The coherency client determines what to cache, what to keep in cache, and what to evict, based on access patterns, coherency server-generated advice, and local statistics (recency- and frequency-based statistics).
- The coherency client combines the coherency server advice with its own population list, resulting in both short- and longer-term cache population, higher hit ratio, and better storage solution optimization, including application-aware storage.
SAN-based multi-host applications are enabled through the Easy Tier Server SAN storage coherency protocol. With managed coherency, advanced storage-replication functions such as FlashCopy® and remote mirroring are transparently enabled.