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 programs. 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 available 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 continuously in background and yield processor to foreground applications.

Diskeeper also offers a free “lite” version, available for downloading at www.execsoft.com. It is a fully-functioning defragmenter, but lacks the scheduling features of the workstation 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 fragmentation 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 directories 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 Mountain 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.

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