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Chapter 5. Additional Topics 53
Extensive testing would be necessary to verify PCI bus functions with the FSI adapter
cards in this environment. This has not been done.
5.13 SCSI adapter for the ThinkPad
Potentially, one might provide an SCSI interface to the ThinkPad and connect external SCSI
tape drives. The supported ThinkPad models do not have this capability, but there are
third-party PCMCIA cards that might be used. We did not attempt to use a SCSI PCMCIA
adapter during our projects. If you require this function, we suggest you contact your
business partner or FSI.
5.14 Disk fragmentation
The raw disks used with UnixWare-based EFS to hold emulated S/390 volumes have a
unique advantage. A raw disk is contiguous space on a hard disk drive. Linux file systems
do not necessarily provide contiguous space for Linux files. After a Linux file system has
been used for normal file creation, deletion, and general operations, it would be unusual for a
large file (such as an emulated S/390 volume) to be created in contiguous space in the file
system.
FLEX-ES performance benefits from contiguous disk space for an emulated volume.
FLEX-ES typically performs Linux disk operations in units of a full track for the emulated
volume. For an emulated 3390, this would be 57 KB. If the data is fragmented in different
areas of the Linux file system, the I/O operation takes longer.
The standard Red Hat 7.1 distribution does not contain a standard defrag command.
Several defrag-type utilities are available from various Web sources; we did not have the time
or resources to thoroughly test any of these and did not use them.
We took the following approach:
A file system performs contiguous file creation when the file system is new.
We placed S/390 volumes in separate file systems (/s390 and /s391).
Generally, we did not place anything else in these file systems. (There are always
exceptions, of course, and several of our backup/restore methods used files in these file
systems.)
The slight fragmentation caused by, for example, deleting three (discontiguous) 3390-1
volumes and creating a 3390-3 volume is not significant.
More work is needed to understand the effects of fragmentation on FLEX-ES operation and to
document techniques to avoid problems in this area.
5.15 Backup and restore considerations
Since a typical
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ThinkPad/EFS cannot directly connect to tape drives, the backup options
are more limited than for a Netfinity/EFS system. Still, backing up and restoring S/390 data
has interesting variations. The most basic element involved is where to store your backup
data. There are several options:
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A ThinkPad/EFS system might use remote FLEX-ES resources to connect to a machine that does have attached
tape drives. This should work (although we did not try it), but cannot be considered a typical ThinkPad/EFS
environment.