PERFORMING A NORMAL BACKUP EVERY NIGHT ENABLES YOU TO RESTORE THEENTIRE SYSTEM USING ONLY A SINGLE NIGHT’S BACKUP TAPE
5.
Correct Answers: E
A. Incorrect:
Performing a normal backup every night enables you to restore the
entire system using only a single night’s backup tape. However, it uses more tape
backup media than is necessary because every file on the system is backed up
every night.
B. Incorrect:
The incremental backup makes a copy of all files marked with the
archive attribute. After each file has been backed up, the file’s archive attribute is
cleared. Therefore, the incremental backup copies only files that were modified
since the last backup. Performing only incremental backups would require restor-
ing every single backup ever made in the event of a hard disk failure.
C. Incorrect:
The differential backup makes a copy of all files marked with the
archive attribute. Unlike the incremental backup, the differential backup does not
modify the archive attribute of files after creating the backup. In this way, per-
forming a differential backup every night ensures that every file modified since the
last full backup can be restored. This is useful when combined with a normal
backup, but using only differential backups results in a backup set that grows
larger every night. Therefore, the differential backup does not meet the criteria of
minimizing the backup media used.
D. Incorrect:
This is a common backup strategy, but it does not meet the require-
ment of needing to restore only two sets of backups for a complete system recov-
ery. Each incremental backup copies only those files that were modified since the
prior night’s backup. Therefore, every single incremental backup since the last
normal backup must be restored to ensure total data recovery. For example, if a
normal backup was performed on a Sunday and incremental backups thereafter,
restoring the system on Thursday requires restoring Sunday’s normal backup and
Monday’s, Tuesday’s, and Wednesday’s incremental backups.
E. Correct:
This backup strategy meets all the requirements. Differential backups
copy all files modified since the last normal backup, enabling a maximum of two
separate restores to completely rebuild a file system. For example, if a normal
backup was performed on a Sunday and differential backups thereafter, restoring
the system on Thursday requires restoring only Sunday’s normal backup and
Wednesday’s differential backup.