Databases Reference
In-Depth Information
System Basics
We will begin with a review of the components that make up any hardware platform
and the impact these components have on the overall platform. You'll find the same
essential components under the covers of any computer system:
• Nodes or systems consisting of CPUs (with multiple cores) for executing the basic
instructions that make up computer programs and memory, storing recently ac‐
cessed instructions and data
• Storage or storage cells that typically consist of a combination of disk storage and
device controllers, sometimes also including PCI Flash (such as is present in Exadata
Storage Server cells)
• Interconnects for distributing data to nodes and storage
• Network ports enabling connectivity for business usage and administration
networks
The number, power, throughput, and capabilities of the individual components deter‐
mine the ultimate cost and scalability of a system. Systems and nodes with more pro‐
cessors and cores are typically more expensive and capable of doing more work than
systems and nodes with fewer; systems and nodes containing newer versions of com‐
ponents typically deliver superior capabilities at similar or lower price points than older
versions.
Each system component has its own performance characteristics, including a time to
access and transport data, or a
latency cost
. The latency cost of a component is the
amount of latency the use of that component introduces into the system; in other words,
how much slower each successive level of a component is than its previous level (e.g.,
Level 2 versus Level 1; see
Table 12-1
). Each component also has limited capacity and
most components can use other resources when the demand for their capacity is
exceeded.
The CPU and the Level 1 (L1) memory cache on the CPU have the lowest latency, as
shown in
Table 12-1
, but also the least capacity. Disk has the most capacity but the
highest latency. Note that the capacities for the storage components marked by the * are
typical in balanced server and storage configurations optimized for performance.
There are several different types of memory: an L1 cache, which is on
the CPU chip; an L2 (Level 2) cache on the CPU surface, an L3 cache
on the same board as the CPU (not as widely offered); and main
memory, which is the remaining memory on the system accessible
through the memory bus.
