Understanding Disk Diagnostics
A
hard disk can suddenly bite the dust thanks to a lightning strike, an
accidental drop from a decent height, or an electronic component
shorting out. However, most of the time hard disks die a slow death.
Along the way, hard disks almost always show some signs of decay, such
as the following:
Spin-up time gradually slows.
Drive temperature increases.
The seek error rate increases.
The read error rate increases.
The write error rate increases.
The number of reallocated sectors increases.
The number of bad sectors increases.
The cyclic redundancy check (CRC) produces an increasing number of errors.
Other factors
that might indicate a potential failure are the number of times that the
hard drive has been powered up, the number of hours in use, and the
number of times the drive has started and stopped spinning.
Since about 1996, almost all hard disk manufacturers have built in to their drives a system called Self-Monitoring, Analysis, and Reporting Technology, or SMART.
This system monitors the parameters just listed (and usually quite a
few more highly technical hard disk attributes) and uses a sophisticated
algorithm to combine these attributes into a value that represents the
overall health of the disk. When that value goes beyond some
predetermined threshold, SMART issues an alert that hard disk failure
might be imminent.
Although SMART has been
around for a while and is now standard, taking advantage of SMART
diagnostics has, until now, required third-party programs. However,
Windows 7 comes with a Diagnostic Policy Service (DPS) that includes a
Disk Diagnostics component that can monitor SMART. If the SMART system
reports an error, Windows 7 displays a message that your hard disk is at
risk. It also guides you through a backup session to ensure that you
don’t lose any data before you can have the disk replaced.
Understanding Resource Exhaustion Detection
Your system can become
unstable if it runs low on virtual memory, and there’s a pretty good
chance it will hang if it runs out of virtual memory. Older versions of
Windows displayed one warning when they detected low virtual memory and
another warning when the system ran out of virtual memory. However, in
both cases, users were simply told to shut down some or all of their
running programs. That often solved the problem, but shutting everything
down is usually overkill because it’s often the case that just one
running program or process is causing the virtual memory shortage.
Windows 7 takes this
more subtle point of view into account with its Windows Resource
Exhaustion Detection and Resolution tool (RADAR), which is part of the
Diagnostic Policy Service. This tool also monitors virtual memory and
issues a warning when resources run low. However, RADAR also identifies
which programs or processes are using the most virtual memory, and it
includes a list of these resource hogs as part of the warning. This
enables you to shut down just one or more of these offending processes
to get your system in a more stable state.
Microsoft is also
providing developers with programmatic access to the RADAR tool, thus
enabling vendors to build resource exhaustion detection into their
applications. When such
a program detects that it is using excessive resources, or if it
detects that the system as a whole is low on virtual memory, the program
can free resources to improve overall system stability.
Note
The Resource Exhaustion Detection and Recovery tool divides the current amount of committed virtual memory by the commit limit,
the maximum size of the virtual memory paging file. If this percentage
approaches 100, RADAR issues its warning. If you want to track this
yourself, run the Performance Monitor , and add the % Committed Bytes in Use counter in the Memory object. If you want to see the exact commit numbers, add the Committed Bytes and Commit Limit counters (also in the Memory object).
Running the Memory Diagnostics Tool
Few computer
problems are as maddening as those related to physical memory defects
because they tend to be intermittent and they tend to cause problems in
secondary systems, forcing you to waste time on wild goose chases all
over your system.
Therefore, it is welcome
news that Windows 7 ships with a Windows Memory Diagnostics tool that
works with Microsoft Online Crash Analysis to determine whether
defective physical memory is the cause of program crashes. If so,
Windows Memory Diagnostics lets you know about the problem and schedules
a memory test for the next time you start your computer. If it detects
actual problems, the system also marks the affected memory area as
unusable to avoid future crashes.
Windows 7 also comes with a
Memory Leak Diagnosis tool that’s part of the Diagnostic Policy
Service. If a program is leaking memory (using up increasing amounts of
memory over time), this tool will diagnose the problem and take steps to
fix it.
To run the Memory Diagnostics tool yourself, follow these steps:
1. | Select Start, type memory,
and then click Windows Memory Diagnostic in the search results. The
Windows Memory Diagnostics Tool window appears, as shown in Figure 3.
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2. | Click one of the following options:
- Restart Now and Check for Problems—
Click this option to force an immediate restart and schedule a memory
test during startup. Be sure to save your work before clicking this
option.
- Check for Problems the Next Time I Start My Computer— Click this option to schedule a memory test to run the next time you boot.
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After the test runs (it
takes 10 or 15 minutes, depending on how much RAM is in your system),
Windows 7 restarts and you see (for a short time) the Windows Memory
Diagnostic Tool icon in the taskbar’s notification area. This icon
displays the results of the memory text.
Tip
If
you’re having trouble starting Windows 7 and you suspect memory errors
might be the culprit, boot your machine to the Windows Boot Manager menu .
When the menu appears, press Tab to select the Windows Memory
Diagnostic item, and then press Enter. If you can’t get to the Windows
Boot Manager, you can also run the Memory Diagnostic tool using Windows
7’s System Recovery Options.
