Les,
When you tell BootVis to optimize, it is actually running the built-in
defragmenter via command line interface and defragmenting the files
indicated by BootVis as being loaded during the boot process.
Yes, you should still defrag your hard drive on a regular basis. It will
not "mess up" when BootVis has done.
A little background on Windows XP/BootVis and "prefetching".
Windows XP will automatically "watch" the boot process and will eventually
form a "picture" of what drivers, etc... get loaded during the boot process.
To form this "picture" takes about 3 boots. After Windows XP has this
information, it then uses it to:
a.. Make sure that the files necessary for boot are "optimized". What this
really means is that the files are defragmented.
b.. To perform driver load overlapping.
One of the slow downs with booting in NT4/Win2k was the sequential nature
that drivers were loaded during the boot process. 1 driver would load and
only when it finished would the next one start. Windows XP does things a bit
differently (as you have noticed). It will overlap driver loading - so that
multiple drivers "load" concurrently. This dramatically speeds up the boot
process. The information gathered from watching the boot process is used to
optimize this process.
Windows XP also monitors application launches and stores information about
what files (.exe, dll, data files) are accessed when an application launches
and stores this information in the /prefetch folder. In this folder is a
file called layout.ini as well as xxxxx.pf files for each application.
Approximately every 3 days, Windows XP as part of scheduled tasks (you can't
find it - its a hidden task) will perform a partial defrag on the files
indicated in the layout.ini file. The attempt here is to make sure that
these files are contiguous (as contigous files can be accessed faster). This
partial defrag is done using the command line interface to the built-in
defragmenter and depends on there being a large enough piece of contiguous
free space the size of all of the files indicated in the layout.ini file. If
your system isn't "idle" or if there isn't a large enough piece of
contiguous free space, then this partial defrag will not be performed (this
partial defrag will not create the contiguous free space needed. It depends
on either running a full defrag pass with the built-in defragmenter - which
doesn't do that good of a job of consolidating free space - or running a 3rd
party defragmenter).
Where does BootVis fit into this picture?
Windows XP monitors the boot process over a period of boots - over a period
of time. BootVis is used primarily to diagnose slow boots by identifying
drivers that take a long time to load (can indicate a poorly written
driver). One of the other things that it can be used for is to monitor a
single boot process and to then take that information (exactly the same
information that Windows XP gathers over a period of system boots) and
perform the optimizations to driver loading. One of the other options that
BootVis allows you to "perform now" is the partial defrag of the layout.ini
files.
So, Windows XP does the same thing as BootVis - except over a period of
boots. BootVis just allows you to perform it now.
BootVis isn't something that should need to be run on a frequent basis
(unless you have installed SP1 or updated drivers) as Windows XP will
automatically update on every boot the same information that BootVis
gathers.
- Greg/Raxco Software
Microsoft MVP - Windows Storage Management/File System
Disclaimer: I work for Raxco Software, the maker of PerfectDisk - a
commercial defrag utility, as a systems engineer in the support department.
