Chapter 4. Planning for IBM tape in i5/OS 103
4.4 Parallel and concurrent save and restore
In order to reduce the save window (the time required to save one or multiple objects to a
tape) it is possible to use an i5/OS functionality to save a single object or library to multiple
tape devices at the same time. When you save to multiple devices you can use one of the
following two techniques:
Parallel save The ability to save or restore a
single object, database library or IFS
multiple tape devices from the same i5/OS job.
Parallel save provides the most significant improvement to customers
with Large Database Files.
Concurrent save The ability to save and restore
different objects from a single database
library or IFS directory to
multiple tape devices, or different database
libraries or IFS directories to multiple tape devices at the same time
from different jobs
. Concurrent save provides significant
improvements when saving typical customers’ workloads.
For more information about different System i workloads, refer to 4.3, “Performance” on
Concurrent operations to multiple tape devices probably are the preferred solution for most
customers. The customers must weigh the benefits of using parallel verses concurrent
operations for multiple backup devices in their environment.
When planning for parallel save and restore, you might want to estimate the improvement
from this as compared to traditional save and restore. Since performance of parallel and
concurrent save depends very much on the particular workload, the most reliable way to
estimate it is to test it by saving the customer’s critical application.
However, some customers are not able to test parallel or concurrent save and restore of their
production workload prior to implementing it. For such customers, you can do a rough
estimation by using the performance measurements of typical workloads that were tested in
System i development. The graphs in Figure 4-4 and Figure 4-5 show save and restore data
rates for one LTO2 tape drive comparing to rates of parallel and concurrent save and restore
to 2, 3 and 4 LTO2 tape drives.
104 Implementing IBM Tape in i5/OS
Figure 4-4 Parallel save and restore of Large Database Files
Figure 4-5 Concurrent save and restore of Large Database Files
More information about measurements of parallel save and restore can be found in the
publication, System i Performance capabilities Reference i5/OS Version 5 release 4, available
on the following Web site:
Parallel Save and Restore, Large File,
1,2,3,4 LTO-2 drives
Concurrent Save and Restore, Large File,
1,2,3,4 LTO-2 drives