[mso] Re: Defragging and outlook.pst
- From: "Greg Chapman" <greg@xxxxxxxxxxxxx>
- To: <mso@xxxxxxxxxxxxx>
- Date: Wed, 18 Sep 2002 14:14:06 -0500
Your real solution is to defrag a little more often. The fragmentation
of the file has more to do with how large the file is and how often it
is fragmented rather than where it is stored. Optimization for
localization to a specific region on the disk is pretty much an esoteric
consideration for the problem you describe. Note that cleaning the file
of aged/unwanted goodies and then compacting it occasionally will help
reduce the size of the file and makes the need for writing it in
non-contiguous ways a little less frequent. However, the existance of
the fragments indicate the file is growing on an as needed basis and
really has no unused space to speak of. XP is the best at this so far as
the PST tends to clean up nicely without help when you delete a lot of
messages.
If you're using speeddisk, it sounds as if you might be on a non-9x OS
(okay, written another way, it sounds as if your OS has an NT kernel and
file system). If that's so, be aware that NTFS fragments faster than FAT
and does take a significant performance hit in the early stages of
fragmentation. However, once you get past 10% fragmentation on this file
system, performance degradation occurs at a much lower rate. So your
best investment is simply to regularly defrag the drive on a more
regular basis. Once every week or two should be sufficient.
I rarely worry about the location of files on the disk based on drive
geometry. My preference, where possible, is to keep files that are used
together stored together. That method allows more time to be spent
reading the data from disk instead of losing time to moving the heads
across the platter. There's also this to consider (and it's tough to
explain);
All sectors on a disk are physically the same size. So, on a track that
is closer to the spindle/hub, fewer data segments will be found than the
farthest track from the hub. Since all sectors are the same size and the
outside track of the disk has a larger diameter, this only makes sense.
Therefore, if you want fewer head movements to read the data of a large
file, move this file to the outside of the disk. If the files are small,
though, you can place them wherever you want but its better to try to
save that outside sector for those really large files.
If you're wondering why all those sectors are the same size and how this
wild series of questions about where to store a file come from, consider
this example. Draw a large circle on a piece of paper. For convenience's
sake, make the circle about as large as the bottom of a standard coffee
mug. In the center of the circle, draw a circle about the size of a
quarter and fill it in. Yes, you may use a crayon if that makes this a
fun exercise for you.<g> The little circle represents the spindle or hub
of your disk platter (most hard disks have 3-4 platters). The big circle
is the outside edge of the platter disk.
Now, starting from the spindle area, draw another circle enclosing the
hub that is about a quarter of an inch larger than the hub. Make another
circle enclosing the circle you just made. Keep on doing this until your
last circle is about one quarter inch smaller than the first big circle
you drew. We'll call these tracks for the time being. Before you do
anything else, repeat this same procedure on another piece of paper so
that you now have two pictures of a disk platter.
Okay, with the first picture, draw lines across the disk as if it were a
pie that you were slicing into 8 pieces. Now you should have 8 pie
shaped pieces of disk, each of them broken into little bands about a
quarter inch wide. Those toward the big end of the pie slice are longer
than the ones closer to the center, right? If each of these were to be
considered a sector, it's obvious that some are larger than others and
that they can't all hold the same amount of information if storage is
based on how much room you have (if you have an attic or a basement then
you already know without a doubt that storage space is a function of
size, no matter how you slice the pie<g>). Obviously, this is not an
efficient way to divide the storage.
So with that second picture of a disk, do this: Start from the hub of
the disk and drawa line between the hub and the next circle. Measure
about an inch from that line and draw another line. Do this until you've
divided that inner circle into several similar sized pieces. At the last
line you drew, extend the line to connect it to the next circle out.
Make this longer line much thicker than the rest of your lines so that
you can see it more easily than the rest of the lines you've drawn. In
that new ring, again, draw lines about an inch apart. When you've made
it all the way around, again, draw a thicker line that ties to the next
outermost ring. Repeat this entire procedure until you have made your
way all the way around the outside ring with these little lines.
Now you have a picture of how data is actually stored on your disk. Each
of the sectors are about the same size and each line that extends from
one ring across to the next represents the end of one track and the
beginning of another.
Get the idea? This makes it really easy to tell how much a disk will
hold, too. The formula is based on how many heads (or readable platter
surfaces) multiplied by how many cylinders (tracks) multiplied by how
many sectors per track (or cylinder) multiplied by how many bytes can be
stored in each sector. So a disk with 16 heads, 1024 cylinders, 63
sectors per track and 512 bytes per sector holds 528,482,304 bytes or
(528482304/(1024*1024))= 504 megabytes. BTW, this formula was also the
standard specified in the original IDE drive spec provided by Western
Digital in WD1003. That's right, the original IDE specification only
allowed for a hard disk to be as large as 504 megs. I bought my first
drive of this size in 1994 and paid $320 US for it. Times have certainly
changed...but the math and the logic behind it still hold!
I know, this is much more than you wanted to think about but hang on to
it. You may find it helpful when you try to answer a question like this
for yourself in the future.
Greg Chapman
http://www.mousetrax.com
"Counting in binary is as easy as 01, 10, 11!
With thinking this clear, is coding really a good idea?"
> -----Original Message-----
> From: mso-bounce@xxxxxxxxxxxxx
> [mailto:mso-bounce@xxxxxxxxxxxxx] On Behalf Of Peter Strisik
> Sent: Wednesday, September 18, 2002 11:08 AM
> To: mso@xxxxxxxxxxxxx
> Subject: [mso] Defragging and outlook.pst
>
>
>
> Norton speeddisk 2003 lists files in the order of greatest
> fragmentation when you do an "analyze". Since outlook.pst is
> number one by a mile, I'm wondering if the best solution
> would be to designate it as "files last" or as "files at
> end". Anyone good at harddisk physics?
>
> ............Peter
>
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