Category : HD Utilities
Archive   : STACTECH.ZIP
Filename : 2402.TXT

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STACKER NOTE STACKER NOTE
Title: Third Party Disk Optimization Programs and Stacker
STAC FAX Index #2402 - 2/10/93
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Background.

Writing to disk can cause file fragmentation over time. Third party disk
optimization programs such as Norton Speedisk, PCtools Compress, and VOPT
were designed to optimize (defragment) un-Stacked drives. Their use on Stacker
drives should be avoided. Stacker includes a utility called SDEFRAG to
optimize and defragment a Stacker drive. Note: SDEFRAG will not optimize an
un-Stacked drive.


Why shouldn't I run third party optimizers on a Stacker drive?

Stacker is able to store data more efficiently than DOS by allocating file
storage units at the sector level. A sector, usually 512 bytes, is the
smallest unit of storage that a hard disk controller can write. DOS, on the
other hand, uses fixed size, multi-sector groups (clusters) for file
allocations. A cluster, typically a group of 4 sectors for partitions under
128 MB, is the smallest unit of storage used by DOS. While DOS uses a File
Allocation table (FAT) to allocate the cluster usage in a drive, Stacker
keeps both a cluster FAT and a sector FAT. An Optimization program will read
the FAT to find all the file fragments, then put the pieces together using
contiguous clusters. Since DOS doesn't keep track of individual sectors
like Stacker does, these programs, which existed long before Stacker came
along, were designed to read only a cluster FAT. They were not designed to
read a sector FAT. This is why they should not be used on the Stacker drive.

What if I accidentally run a third party optimizer on a Stacker drive?

Because these programs don't read Stacker's sector FAT, they tend to
fragment a Stacker drive as they assemble the file's pieces in what they
think is a contiguous order. The data remains safe, however, the
optimization process may have created lost sectors. Run the Stacker utility
: SCHECK /F (Stacker 2.0) or CHECK /F (Stacker 3.0) to reclaim these lost
sectors. Then run SDEFRAG to defragment the drive.

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Copyright 1993, Stac Electronics