Single-Level Storage - IBM i series Handbook

iSeries Architecture: Fundamental Strength of the iSeries
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processor continues executing another application program. Nanoseconds (10 second) is
the unit of time used to measure main storage access times. I/O operations are measured in
-3
milliseconds (10 second).
The previous figure shows a high-level overview of the structure of the iSeries 840 model.
Central in the figure is the extremely high speed memory-processor-I/O interconnect switch
at 43.2 GB/sec. This allows for data transfers between components connected to the switch
to proceed at a very high rate. Separate connections to the switch are provided for each
group of six processors, each of four banks of memory, and two connections for I/O traffic.
These independent paths result in much superior performance than previous designs with a
single common shared memory bus path, for which all components contended.
With the new design, there are many paths to the high speed switch, which can operate
separately. Its high bandwidth characteristics allow for connecting source and destination
quickly and efficiently to allow for significant benefit in overall processor speed and system
performance enhancement. This design provides the iSeries server with outstanding
performance in the commercial, transaction-based environment.

Single-level Storage

Application programs on an iSeries server are unaware of the underlying hardware
characteristics, because of the iSeries Layer (or TIMI) (see "Technology Independent
Machine Interface" on page 13). Applications are also unaware of the characteristics of any
storage devices on the system because of single-level storage.
As with TIMI, the concept of single-level storage means that the knowledge of the underlying
characteristics of hardware devices (in this case, main storage and disk storage) reside in the
SLIC. All of the storage is automatically managed by the system. No user intervention is ever
needed to take full advantage of any storage technology. Programs work with objects (see
"Object-based" on page 18). Objects are accessed by name, not by address.
The iSeries server address size is vast. iSeries models can address the number of bytes that
64
64 bits allows it to address. The value 2 is equal to 18,446,744,073,709,551,616.
Therefore, the iSeries models can address 18,446,744,073,709,551,616 bytes, or 18.4
quintillion bytes. To put this into more meaningful terms, it is twice the number of millimeters
in a light year. Light travels at approximately 6,000,000,000,000 miles in one year.
Single-level storage also enables another extremely important iSeries customers benefit,
object persistence . Object persistence means that the object continues to exist in single-level
storage (unless purposely deleted by the customer). Memory access is extremely fast. A
customary machine requires that information be stored in a separate file system if the
information is to be shared or retained for a long time.
Persistence of objects is extremely important for future support of object-oriented databases
for data accessibility and recovery. Objects continue to exist even after their creator goes
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iSeries Architecture: Fundamental Strength of the iSeries