The configuration of the disk peripherals is influenced both by both the load profile and by the time requirements of the application. In practice there are essentially two load types, which can be characterized as follows:
OLTP mode | Batch processing, data backup or other | |
Typical block size per | "small": | "large": |
Indicator | IO rate | Throughput |
Typical input/output | Random access | Sequential access |
The applications in BS2000 can always use block sizes of up to 160 KB for each I/O operation. In the case of NK formating, certain disk models even permit block sizes of up to 480 KB. This enables the throughput to be increased significantly.
Depending on the application type, different performance targets are focused on.
High throughput is aimed for in the case of data backup and in batch mode.
In OLTP mode, good response times are expected.
The I/O operations play an important part in the throughput rate/dwell time and the response time/transaction time (see section Time slices for I/Os to disk).
Standardized load types
In this manual the performance observations relate to the following standard load cases:
"Sequential Write", "Sequential Read". This corresponds to throughput-oriented loads in the case of data backups or batch processing.
"Random Read", "Random Write". This corresponds to IO-oriented OLTP loads, where response time is critical.
"Random25" random accesses with a proportion of 25% write and 75% read I/Os. With small blocks this case reflects OLTP mode.
While "Random25" is a load which is close to practical application and is interesting above all for measurements, the theoretical information in this chapter is restricted to pure reads or writes.