STORE and TurboSTORE/iX Products Manual (B5151-90003)

Chapter 3 37
Preparing Storage Devices
Preparation Process
Selecting the Backup Method
The best way to use your backup devices depends upon the characteristics of the files that
you are storing, your needs for compatibility with other versions of MPE, and your system
configuration.
The characteristics of the set of files help determine choices (or options) for storing them.
Generally speaking, the more files being stored, the more it is to your advantage to use
multiple devices. If you are storing only a few files of moderate size, one backup device may
be sufficient. If you are storing many files (for example, all the files in an account, or a
smaller number of very large files), using a multiple-device backup is probably to your
advantage.
Your needs for compatibility with other versions of MPE limit your choices. If you need to
produce STORE backups that are compatible with MPE V/E using the TRANSPORT
parameter, you can only store files to a single device.
If you are not creating tapes for use by MPE/V, then your system configuration is the most
important determinant of which multiple-device backup method to use. Use the following
guidelines to select a method:
Which and How Many Backup Devices Do You Have?
Which devices you may use for a multiple-device backup are described in this chapter.
Obviously, to use sequential or parallel devices, you must have at least two backup devices.
If you have two or three devices, you may use either parallel or sequential devices. If you
have three or more devices, you may use two or more parallel device pools.
If you want to use magneto-optical devices or disk files, refer to the sections "Preparing
Magneto-Optical (MO) Disks" and "Storing to Disk Files" later in this chapter. If you are
using StorageTek devices, most of the guidelines for tape and DDS devices will apply.
If you are using StorageTek devices, you should follow the directions for tape and DDS
devices. However, note that due to the higher throughput of these devices, they should be
configured on your system for maximum performance. Refer to the Configuration Guide
(put real name there) for information on the proper configuration for 3480 devices.
Selecting Backup Device Order
Once you have determined how many devices you are going to use for your backup, you
should determine the order of each device in the backup. Assign each device a position
based on its logical device (LDEV) number.
Use the chart in Figure 3-1. to help you assign your devices. Select one of the methods in
the chart, and then write in the LDEV numbers of each device you plan to use in the order
that you plan to use it. For example, if you intend to use two parallel devices, write in the
LDEV number of the first device next to Device A and the LDEV number of the second
device next to Device B in the Parallel section of the chart. It may be helpful for you to
photocopy the chart and use it as a guide whenever you use a multiple-device method to
store files.