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SSD Cache
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10. SSD Cache
This chapter describes an overview and operations of SSD cache. Now we provide two
cache types, SSD read cache and read-write cache.
INFORMATION:
SSD cache 2.0 with read and write cache is available in SANOS firmware
1.1.0.
10.1. Overview
Traditionally, data has been stored on traditional rotating memory, or HDDs (Hard Disk
Drives) and SSDs (Solid-State Drives) are mainly used for mission-critical applications that
demand high-speed storage systems, however tend to be costly. In recent years, the
capacity of HDDs has increased, but their random I/O (Input / Output) has not kept pace. For
some applications such as web commerce, clouds, and virtualization that require both high
capacity and performance, HDDs, though capacious, simply are not fast enough and SSDs
have increased capacity and have declined in cost, making them more attractive for caching
in SAN storage networks.
Smart Response Technology (also known as SSD cache technology) leverages the
strengths of both HDDs and SSDs, to cost-effectively meet the capacity and performance
requirements of enterprise applications. Data is primarily stored on HDDs while SSDs serve
as an extended HDD memory cache for many I/O operations. One of the major benefits of
using SSD cache is the improved application performance, especially for workloads with
frequent in I/O activity. The read data of an application that is frequently accessed is copied
to the SSD cache; the write data that is stored to the SSD cache temporary and then flush to
HDDs in bulk. So the application receives an immediate performance boost. QSAN SSD
cache enables applications to deliver consistent performance by absorbing bursts of
read/write loads at SSD speeds.
Another important benefit is improved TCO (Total Cost of Ownership) of the system. SSD
cache copies the hot or frequency of data to SSDs in chunks. By offloading many if not most
of the remaining IOPS after SSD cache, the user can fill the remainder of their storage needs
with low cost, high capacity HDDs. This ratio of a small amount of SSD paired with a lot of
HDD offers the best performance at the lowest cost with optimal power efficiency.