Database Reference
In-Depth Information
Chapter 12
Tuning the Storage Subsystem
Decisions about how to design or configure storage hardware and software should be centered on what kind of
performance is required from the I/O subsystem. This depends on the type of application, supported workload
characteristics, service level agreements (SLA), and so forth. However, due to factors such as cost, reliability,
availability, power, and ease of use, performance is often neglected and does not meet expectations. Trade-offs are
often made between cost and performance, ease-of-use and performance, and consolidation and performance.
Trade-offs at the cost of performance are made in all tiers of the storage layer (not to mention in other areas of the
infrastructure, such as network and processor speeds). File-cache management, file-system architecture, and volume
management translate application calls into individual storage access requests. These requests traverse the storage
driver stack and generate streams of commands that are presented to the disk subsystem. The sequence, type, and
number of calls and the subsequent translation can improve or degrade overall performance of the I/O subsystem.
Good planning of the storage topology and data layout for throughput or response times can make the difference
between excellent workload and application performance and having poor workload with high response times that
result in poor application performance.
Choosing Storage
The basic function of storage systems is to provide storage resources to the servers for primary datastore, for mirrored
datastore, or for backup datastore. A wide variety of storage systems are available in the marketplace and serve
different purposes, with varied performance characteristics and features. The storage devices include RAID disk
arrays, Just a Bunch of Disks (JBOD), tape systems, and so on. The types of interfaces provided on these devices
include SCSI, fiber channel, and Ethernet.
The most important considerations in choosing storage systems include the following:
•
Understanding business needs for high availability of data, data protection, performance, and
data recovery
•
Understanding the characteristics of current and future storage workloads
•
Understanding the application behavior and access patterns for planning and performance
requirements
•
Understanding necessary storage space, bandwidth, and latency requirements for the current
and future growth of business
•
Understanding business needs for data layout, such as striping, redundancy, and backup
strategy
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