Category : Tutorials + Patches
Archive   : TEC999.ZIP
Filename : TEC009.DOC

-----------------------------------------------------------------------
STACKER NOTE Stac Electronics Technical Note

Subject: Stacker and Disk Caching Programs.

Tec009 - 6/18/92
_______________________________________________________________________

Stacker has been tested with most popular disk caching programs such as
Smartdrive, PC-KWIK, PC-Cache, Norton Cache, and HyperDisk and has been found
to be compatible. These programs will not cache the Stacker drive directly,
but they will process the physical drive which hosts its companion Stacvol
file. By caching this file's compressed data, the cache size is effectively
doubled.

Q: Do I need to tell the cache not to process the Stacker drive ?

A: Most disk caching programs will detect the Stacker logical drive and will
not cache it by default. Any attempt to force it to cache the Stacked
drive may result in a message such as "unable to cache specified drive".
Therefore, if you are given the option, specify that the host drive be
cached. You can determine the Stacker host drive by using the Stacker
command. Type STACKER : It will bring up a drive map line that
looks something like this:

Drive C: was Drive D: at boot time [D:\STACVOL.DSK]

In this example, D: is the host drive. Therefore, you would specify that
D: be cached and not C:. If the cache loads in Config.sys, load it before
the Stacker device driver to ensure host drive caching.

Q: How do I cache a "replaced" Stacked drive or removable ?

A: A "replaced" Stacker drive is one which has replaced its letter with that
of the host drive. Removable drives such as floppies, Bernoullies and
Syquest drives are mounted this way. In order to cache these replaced
drives, they must be mounted and replaced after the cache has been loaded.

This can be done by:
1. Placing the cache device driver before the Stacker device if loading in
Config.sys.
-OR-
2. If the cache loads in Autoexec.bat, add a @ to the Stacker device
driver in Config.sys for each drive you wish to replace. Then, in
Autoexec.bat, AFTER the command to load the cache, mount each drive
with Stacker x: where x: is the drive you wish to mount as
replaced.

Q: Is it safe to use a cache's write delay feature with Stacker ?

A: Most caches, such as the new SMARTDRIVE 4.0, incorporate a write delay
feature. A write delay, also known as a write back or lazy write, causes
the data to be held in memory for a period of time before it gets stored
to disk. Therefore, if a machine hangs or is rebooted before the
information is written, data is lost and possibly corrupted. A Stacker
drive will not increase the likelihood of file corruption occurring,
however, it is just as susceptible as any other DOS drive. It is up to
the individual user to determine if the extra speed is worth the risk.
The write delay feature is usually selectable, and can therefore be
disabled. For example, with SMARTDRIVE 4.0 disable write caching by
placing the host drive letter ONLY on the command line:

i.e. SMARTDRV.EXE d where d is the host drive letter

Q: Can I use Stacker's cache with other caches?

A: Stacker's cache can be setup in EMS or conventional memory. The 64K EMS
cache will provide caching benefits and greatly reduce the Stacker device
memory requirements. Alternatively, a conventional memory cache of 0 to
64K can be setup with a /m= parameter on the Stacker device driver.
Unlike the EMS cache, this adds directly to the size of the driver. The
default for the conventional memory cache size is 0 K. Both caches are
compatible with third party caches but due to their relative small size,
their contribution is negligible. Because of this, in the presence of
another cache there is really no need to enable the Stacker cache unless
a reduction in driver size is desired.
-----------------------------------------------------------------------------
1992 Stac Electronics