Recognizing a Data Loss Situation
A data loss situation is usually characterized by the sudden
inability to access data involving a previously functioning
computer system or backup or the accidental erasure of data
or overwriting of data control structures.
This section outlines the major symptoms of data loss. What
to do and what NOT to do when experiencing data loss is covered
under upcoming section "The Data Recovery Process: What to do First"
Common Data Loss Situations
Floppies
A floppy disk has become un-readable. The error message says
something like this: "A:\ is not accessible. The device is not ready.
This diskette is not formatted. Would you like to format now?"
Check to see if this condition persists after trying to read the
problem floppy disk in a different floppy drive.
Single Hard Drives From Notebooks and Desktop PCs
General Symptoms of Computer Problems
- Intermittent freeze-ups, keyboard or mouse malfunctions,
blank or flickering displays or an inability to access networked
resources may be symptoms of computer problems that
are not data loss situations. A call to your local technical
support person at a computer store or corporate help desk
is recommended as long as they do nothing during their
troubleshooting that will risk hurting your data.
- A simple problem that can stump beginners or casual
users is "no power up." Check to see if the PC is plugged
in and the wall socket is working or if the internal power
supply inside the computer has failed.
Typical Symptoms/Characteristics of a Common Data
Loss Situation
- Accidental deletion of data.
- Accidental reformatting of partitions.
- Hard disk crash or hard disk component failure.
- Ticking or grinding noises coming from the system unit where
the hard drive is located while powering up or trying to access
files. This symptom almost always indicates a failing hard
drive and is often accompanied by some of the other symptoms.
Note: Most drives will emit a light mechanical hum that a user may notice
under normal operation. An indication of impending failure is when the
"normal sound" changes to louder ticking or grinding noises. This symptom
may precede actual data access problems as the drive utilizes spare sectors.
- Computer won't boot. Blue or black screen after power up.
The system will not load Windows (or other O/S).
- Applications that are unable to run or load data:
- Trying and failing to start an application such as
Microsoft® Excel® or Microsoft® Word®.
- Trying and failing to load a file while running Excel or Word.
- Opening folders that should be full of files but appear empty.
- Inaccessible drives and partitions.
- Corrupted data.
- Visible fire or water damage.
- Media surface contamination and damage.
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Complex Data Loss Situations
Note that individual media in servers can suffer from all the
same issues detailed in the preceding section. Include the previous
list of symptoms while diagnosing complex data loss situations.
Servers
Including single drive, RAID, NAS and JBOD type servers.
- Server crash during operation or power up.
- Server will not reboot after "routine" upgrade to operating
system or applications.
- Server reboots but cannot access or even "see"
attached storage.
- Boot drive problems regarding losing critical configuration data.
- RAID controller failure rendering drives inaccessible.
- Hard drive failed.
- Failed restore.
- RAID alarm ignored.
- Server registry configuration lost.
- Intermittent drive failure resulting in configuration corruption.
- Accidental reconfiguration of RAID drives.
- Multiple drive failure.
- Accidental replacement of hard drive.
Tape Media
- Corrupted tape headers:
- Tape appears empty of data (blank) but should be full.
- Tape should be full but has very little data with an early
End-of-Data (EOD) marker.
- Accidental overwriting of headers renders the tape
invisible or inaccessible to the restore program.
- Accidental reformatting or erasure of tape.
- Tape has become un-spooled inside the cartridge.
- Obvious physical damage.
- Tape media stretched, snapped or split.
- Visible fire or water damage.
- Media surface contamination and damage.
- Tape cannot be read past a worn-out or contaminated area.
- Tape backup software corruption.
Optical Media
- Sector read errors preventing access to certain files.
- Message: "This disk is not formatted. Would you like to
format now?"
- Corrupted filesystem structures show empty or invalid
(e.g. FAT, directories, partition entries).
Auto-loaders and Jukeboxes
Both optical and tape media libraries or multi-volumes can
be maintained through automation. To secure an archival
copy, an (offsite) backup copy or for other reasons, rotations
are required by the technicians to cycle the media in and out
of the autoloaders. As these can be complex systems, any
rotational error can cause data to be over-written or incorrect
EOD markers to be written to the tape.
Corrupted/Damaged Databases and File Systems
- The database is locked as "suspect," preventing access
and it cannot be restored to a functional state.
- The file header tables have been "dropped," deleted
or recreated.
- Backup files not recognizable by database engine.
- Accidentally overwritten database files.
- Accidentally deleted records.
- Corrupted database files or records.
- Damaged individual data pages.
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