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Change the defaults for newfs to disregard the geometry in the disklabel.

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We pretend we have one head with two megabyte worth of sectors per cylinder.

The code try to access another head in what it belives to the same
physical cylinder, because it belives that it would be faster than
waiting for the next free sector under this head to come around.

Most modern drives doesn't have a "classical" geometry, and thus
we end up fooling ourselves doing the above optimization.  With this
change we will fill a cylinder sequentially if we can, and thus get
much more mileage from the track-buffer/cache built into the drives.

As a result a lot of seeks to the next or previous track should be
avoided by this.

(My disk is a lot less noisy actually...)

You can still get the old behaviour, by specifying zero for the
numbers.

This will also solve the problem with newfs barfing at really big
drives.

Obtained from:	adult advice from Kirk.
This commit is contained in:
Poul-Henning Kamp 1995-02-05 08:42:31 +00:00
parent 0bc786d076
commit 55abc5794a
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=6192
2 changed files with 18 additions and 4 deletions
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7
sbin/newfs/newfs.8
View File

@ -87,8 +87,7 @@ or
the disk must be labeled using
.Xr disklabel 8 .
.Nm Newfs
builds a file system on the specified special device
basing its defaults on the information in the disk label.
builds a file system on the specified special device.
Typically the defaults are reasonable, however
.Nm newfs
has numerous options to allow the defaults to be selectively overridden.
@ -232,9 +231,13 @@ The speed of the disk in revolutions per minute.
.It Fl t Ar #tracks/cylinder
The number of tracks/cylinder available for data allocation by the file
system.
The default is 1.
If zero is specified, the value from the disklabel will be used.
.It Fl u Ar sectors/track
The number of sectors per track available for data allocation by the file
system.
The default is 4096.
If zero is specified, the value from the disklabel will be used.
This does not include sectors reserved at the end of each track for bad
block replacement (see the
.Fl p

15
sbin/newfs/newfs.c
View File

@ -144,13 +144,24 @@ void fatal();
*/
#define NRPOS 1 /* number distinct rotational positions */
/*
* About the same time as the above, we knew what went where on the disks.
* no longer so, so kill the code which finds the different platters too...
* We do this by saying one head, with a lot of sectors on it.
* The number of sectors are used to determine the size of a cyl-group.
* Kirk suggested one or two meg per "cylinder" so we say two.
*/
#define NTRACKS 1 /* number of heads */
#define NSECTORS 4096 /* number of sectors */
int mfs; /* run as the memory based filesystem */
int Nflag; /* run without writing file system */
int Oflag; /* format as an 4.3BSD file system */
int fssize; /* file system size */
int ntracks; /* # tracks/cylinder */
int nsectors; /* # sectors/track */
int ntracks = NTRACKS; /* # tracks/cylinder */
int nsectors = NSECTORS; /* # sectors/track */
int nphyssectors; /* # sectors/track including spares */
int secpercyl; /* sectors per cylinder */
int trackspares = -1; /* spare sectors per track */