The LA Fox Developer Newsletter

January 1997

Disk Fragmentation (Con’t from page 3)

Defragmenters have been available for FAT volumes for years,

and one is included with Windows 95. When Windows NT was

first released, there were no defragmenters available. Microsoft

originally claimed that fragmentation was not a serious problem

under NT, particularly on NTFS volumes. Unfortunately, this is

not true. From my experience, fragmentation can actually be a

much worse problem on a computer running Windows NT than

on one running Windows 95 or DOS. Microsoft has finally

admitted the problem, and built ‘hooks’ into NT 4.0 to make it

easier to defragment disks, even when files are in use.

The primary reason why fragmentation is particularly severe

under NT is that, unlike previous versions of Windows, it does

not allow directories to be moved at all. In addition, if the

volume is formatted as NTFS, the operating system reserves

one or more large areas on the disk for the Master File Table,

which also cannot be moved. As a result, it is impossible for a

defragmenterto move all files and directories to the beginning of

the volume to consolidate the free space. At a minimum, the

possible free space areas on a FAT or NTFS volume on an NT

machine will be permanently divided into nearly as many

fragments as you have directories on the volume.

How bad is the problem? Two recent experiences with my NT

Server laptop with a 1.3 gig drive should illustrate. In order to do

a client/server demo, I copied a VFP database and tables

occupying 120 Mb to the laptop. I then ran the VFP upsizing

wizard to create a 200Mb SQL Server database containina the

same data. Performance was very slow, which I attributed to

overloading the 100 MHz processor. Later, I ran a defragger and

discovered that the largest VFP table (70 megs) and the SQL

Server database were in over 200 fragments each. After

defragging, performance nearly thpled.

Later I deleted those databases and installed some new pro-

grams. Then I copied an updated version of the DBF files to the

laptop. I ran a disk analysis, whose partial results were:

The largest DBF file (80 megs) was in an incredible 10,087

fragments. A second 20 meg table was in 2,454 fragments.

Imagine what the performance would be doing a SQL SELECT

on those tables!

Another potential performance problem is a fragmented swap

file. If you expand the size of the swap file on a heavily used

volume, it may become fragmented. I found a swap file on one

client’s server in 700 fragments. Since swap files cannot be

moved either, the best solution is to move the swap file to a

different drive temporarily, defragment the drive it was on, then

recreate it on this drive.

At press time (January 1997) there are 2 defragmenters avail-

able for Windows NT. Diskeeper from Executive Software, has

been out for 2 years. The workstation version lists for $125

(street price lower). The $399 server version can remotely

defrag all NT workstations connected to the network, as long as

they have a copy of the workstation product installed. Both

versions can be scheduled to run at off times, or will run con-

tinuously in background and yield processor to foreground

applications.

Diskeeper also offers a free “lite” version, available for down-

loading at www.execsoft.com. It is a fully-functioning

defragmenter, but lacks the scheduling features of the worksta-

tion and server versions.

Symantec also has a free beta version of the Norton Speed Disk

for NT available at www.symantec.com. The beta version will

not work after 2/15/97, by which time the full product should be

available for purchase (pricing is not yet available).

These products perform essentially the same functions, and do

a good job of keeping you entertained with graphical fragmenta-

tion displays. Assuming there is sufficient free space available,

they will completely defragment most files. In some cases it

may be impossible to completely defrag afew large files

because there are no contiguous free spaces large enough to

hold the entire file. In addition, these defraggers will relocate

numerous smaller files to fill in the small gaps between directo-

ries completely, thus minimizing the number of small free space

fragments and leaving larger blocks of free space elsewhere.

They will defrag both FAT and NTFS volumes.

Rather than doing a performance and feature comparison here, I

recommend you download and install both of these products,

and see which you like better. While you are at it, be sure to

peruse the excellent documentation available on the

www.execsoft.com site, which provides a good description of the

way data is stored by NT and of how defragmenting programs

deal with some of the limitations described earlier.

fEd. Note: Jim Slater is the Executive VP of the Rocky Moun-

tain Fox Users Group in Denver. He has been developing in

dBase and Foxpro for 12 years, was a beta tester for VFP 3.0

and 5.0, and is a Microsoft MVP. Jim can be reached on CIS at

76367,1735 or on the Internet atSlaterJ@ix.netcom.com.J

Did You Know? If you’re planning a trip to Myanmar(whereve

that is) leave the modem at home - as well as the fax machine,

ISDN adapter, and any thoughts of starting up a network. The

military government prohibits the ownership, use, import, or

borrowing of any devices or technology it deems harmful to

state security, national unity, yada-yada-yada. Anyone who

runs afoul of the Computer Science Development Law risks up

to 15 years in prison.

Page 4