kkerce@x102c.harris-atd.com (Kingsley F. Kerce) (07/04/89)
As I understand it, MS-DOS's BUFFERS entry in `config.sys' reserves memory for information read from disks, and the FASTOPEN command "tracks" the location of files on disks, holding hard pointers (to the location of the files) in memory. It seems that the functionality of BUFFERS and FASTOPEN is duplicated if one uses a disk caching scheme. Comments? -- |=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=| Kingsley Kerce | kkerce%x102c@trantor.harris-atd.com | Harris Corp. GISD | uunet!x102a!x102c!kkerce | PO Box 98000 MS W2/7744 (407)984-6623 | | Melbourne, FL 32902
stephen@ziebmef.uucp (Stephen M. Dunn) (07/11/89)
In article <KKERCE.89Jul3205043@x102c.harris-atd.com> kkerce@x102c.harris-atd.com (Kingsley F. Kerce) writes:
$As I understand it, MS-DOS's BUFFERS entry in `config.sys' reserves
$memory for information read from disks, and the FASTOPEN command
$"tracks" the location of files on disks, holding hard pointers (to the
$location of the files) in memory.
Yes, that's pretty much correct. DOS's buffers hold information which has
been read in from the disk (we'll just consider a read-only example for simplicity's
sake). This could include directory and/or FAT information, and the actual
data from a file. FASTOPEN stores part or all of the directory and subdir-
ectory structure of one or more disks in memory so that files can be opened
without actually reading from the disk.
$It seems that the functionality of BUFFERS and FASTOPEN is duplicated
$if one uses a disk caching scheme.
Partially. Sometimes, the buffers will hold the required directory information.
The FASTOPEN command always holds the directory information, but never
contains the files themselves. A disk cache is like a large number of
buffers, essentially. It holds the most recently used disk blocks, which may
or may not include directories, FAT entries, subdirectories, and files. Often,
the disk cache will perform read-ahead. This means that if you access one
particular sector, it will guess that there is a good chance that you will
soon read the next few sectors and it will read them into memory all at once.
One advantage of most disk-cache programs is that they will generally use
extended or expanded memory if you want them to, whereas DOS's buffers won't
(with the exception of DOS 4, which will use EMS).
--
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! Stephen M. Dunn stephen@ziebmef.UUCP ! DISCLAIMER: Who'd ever !
! My puppy died late last fall ! claim such dumb ideas? !
! He's still rotting in the hall (O.E.) ! I sure as heck wouldn't !