Appendix D Maintaining The System; Data Preservation; Scheduling Backups; Backup Devices - Dell Precision 400 User Manual

Appendix D
Maintaining the System
P
roper use of preventive maintenance procedures can
keep the system in top operating condition and minimize
the need for costly, time-consuming service procedures.
This appendix contains maintenance procedures that you
should perform regularly.
D
ata Preservation
Everyone inadvertently deletes files at one time or
another. Also, hard-disk drives can fail after extended
use, so it is not a question of whether you will eventually
lose data, but when. To avoid such loss of data, you
should regularly make backup copies of all hard-disk
drive files. Frequent, regular backups are a must for any-
one using a hard-disk drive.

Scheduling Backups

The frequency with which backups should be made
depends on the amount of storage space on a hard-disk
drive and the volatility of the data contained on the drive.
Heavily used systems require more frequent backups
than systems in which files are seldom changed.
Dell recommends that you back up the hard-disk drive at
least once a week, with a daily backup of those files
known to have been changed. Following these guidelines
ensures the loss of no more than a day's work in the event
of a hard-disk drive failure or if you inadvertently delete
one or more important files.
As further insurance against data losses, you should keep
duplicate copies of the weekly and monthly backups at an
off-site location. Doing this ensures that you lose no
more than a week's work, even if one of the on-site back-
ups becomes corrupted.

Backup Devices

Tape drives are fast, convenient, and affordable devices
that can back up data at rates of up to 1.6 megabytes per
second (MB/sec) (sustained, with data compression) and
can often run unattended. Dell offers tape drives with
storage capacities in the range of 200 MB to 8 gigabytes
(GB) per tape cartridge and recommends these drives and
their associated backup software for use as system
backup devices.
As a last resort, you can back up a hard-disk drive's con-
tents on diskettes, a method that is both time-consuming
and prone to human error. Also, backing up a full
540-MB hard-disk drive requires approximately 375 dis-
kettes (when using 1.44-MB diskettes). Therefore, if it is
absolutely necessary to use diskettes as backup devices,
any unwanted hard-disk drive files should be deleted
before a backup procedure is started.

Recovering Data

Some hard-disk drive failures are recoverable. In these
cases you may be able to recover all lost data if the
proper utility software is available. Even losses such as
accidentally deleted files or accidental reformatting of a
hard-disk drive can be reversed with these utilities.
If the computer system is running MS-DOS, many appar-
ent data loss problems are due to corruption or erasure of
the hard-disk drive's master boot record (MBR),
MS-DOS boot sector, or file allocation table (FAT). That
is, accidental deletion of files or accidental reformatting
of the hard-disk drive alters the MS-DOS boot sector, the
FAT, and the root directory.
However, such accidents do not actually erase the con-
tents of the hard-disk drive files until new data is written
to the sectors containing these files. With software such
as the Norton Utilities, Mace Utilities, or PC-Tools
Maintaining the System D-1