disktab for VPC Disk
- From: "H.Tomaru" <nospam@xxxxxxxxxx>
- Date: Fri, 07 Oct 2005 00:26:18 +0900
I'm trying to optimize the disk access of NEXTSTEP on Virtual PC 5.0.4.
Could anyone tell me the best value of, e.g., #tracks/cylinder, #cylinders/group,
revolutions/minute, sector-size? Are these values insignificant in VPC?
Maximum size of NeXT file system is 2GB.
The followings are man pages of newfs, disktab, tunefs in NEXTSTEP:
% man - newfs
NEWFS(8) UNIX Programmer's Manual NEWFS(8)
NAME
newfs - construct a new file systemSYNOPSIS
/usr/etc/newfs [ -N ] [ -v ] [ -n ] [ mkfs-options ]
character-device [ disk-type ]DESCRIPTION
Newfs is a ``friendly'' front-end to the mkfs(8) program.
Newfs will look up the type of disk a file system is being
created on by using the information contained in the disk
label of the character-device. If the disk-type argument is
specified the information in the disk description file
/etc/disktab is used. This disk information is used to cal-
culate the appropriate parameters to use in calling mkfs,
then build the file system by forking mkfs and, if the file
system is a root partition, install the necessary bootstrap
programs in the initial 8 sectors of the device. The -n
option prevents the bootstrap programs from being installed.
The -N option causes the file system parameters to be
printed out without actually creating the file system. If the -v option is supplied, newfs will print out its
actions, including the parameters passed to mkfs. Options which may be used to override default parameters
passed to mkfs are:-s size The size of the file system in sectors.
-b block-size
The block size of the file system in bytes. -f frag-size
The fragment size of the file system in bytes.-t #tracks/cylinder
-c #cylinders/group
The number of cylinders per cylinder group in a
file system. The default value used is 16. -m free space %
The percentage of space reserved from normal
users; the minimum free space threshold. The
default value used is 10%. -o optimization preference (``space'' or ``time'')
The file system can either be instructed to try to
minimize the time spent allocating blocks, or to
try to minimize the space fragmentation on the
disk. If the value of minfree (see above) is less
than 10%, the default is to optimize for space; if
the value of minfree greater than or equal to 10%,
the default is to optimize for time. -r revolutions/minute
The speed of the disk in revolutions per minute
(normally 3600). -S sector-size
The size of a sector in bytes. -i number of bytes per inode
This specifies the density of inodes in the file
system. The default is to create an inode for
each 2048 bytes of data space. If fewer inodes
are desired, a larger number should be used; to
create more inodes a smaller number should be
given.FILES
/etc/disktab for disk geometry and file system partition
information
/usr/etc/mkfs to actually build the file system
/usr/standalone/boot for boot strapping programsSEE ALSO
disktab(5), fs(5), disk(8), diskpart(8), fsck(8), format(8),
mkfs(8), tunefs(8) M. McKusick, W. Joy, S. Leffler, R. Fabry, ``A Fast File
System for UNIX'', ACM Transactions on Computer Systems 2,
3. pp 181-197, August 1984. (reprinted in the System
Manager's Manual, SMM:14)
% man - disktab
DISKTAB(5) UNIX Programmer's Manual DISKTAB(5)
NAME
disktab - disk description fileSYNOPSIS
#include <sys/disktab.h>DESCRIPTION
Disktab is a simple data base which describes disk
geometries and disk partition characteristics. The format
is patterned after the termcap(5) terminal data base.
Entries in disktab consist of a number of `:' separated
fields. The first entry for each disk gives the names which
are known for the disk, separated by `|' characters. The
last name given should be a long name fully identifying the
disk. The disk(8) program writes this information to the label
area of a disk when it is initialized. The getdiskbyname(3)
and getdiskbydev(3) routines may be used to read this infor-
mation from the data base or disk label respectively. The following list indicates the normal values stored for
each disk entry.Name Type Description
ty str Type of disk (e.g. removable_rw_optical)
ns num Number of sectors per track
nt num Number of tracks per cylinder
nc num Total number of cylinders on the disk
pa-h num Base sector number of partition [a-h]
sa-h num Size of partition [a-h] (sectors)
ba-h num Block size for partition [a-h] (bytes)
fa-h num Fragment size for partition [a-h] (bytes)
ca-h num Partition "cylinders-per-group" for newfs
da-h num Partition density ("bytes-per-inode") for newfs
ra-h num Partition "minfree" for newfs
oa-h str Partition optimization ("space" or "time") for newfs
ia-h bool Run newfs(8) on partition during initialization with disk(8)
ma-h str Partition mount point name
aa-h num Partition auto-mount on insert
ta-h str Partition file system type ("4.3BSD", "sound" etc.)
rm num Rotational speed in rpm (3600 default)
ss num Sector size in bytes
fp num Number of sectors in "front porch" of disk
bp num Number of sectors in "back porch" of disk
ng num Number of alternate groups on the disk
gs num Number of sectors per alternate group
ga num Number of alternate sectors per alternate group
ao num Sector offset of alternates in alternate group
os str Name of file to boot from
z0-1 num Locations (block number) of first level boot code
hn str Hostname
ro char Read only root partition (e.g. 'a')
rw char Read/write partition (e.g. 'b')
FILES
/etc/disktabSEE ALSO
disk(8), newfs(8), getdiskbyname(3), getdiskbydev(3)% man - tunefs
TUNEFS(8) UNIX Programmer's Manual TUNEFS(8)
NAME
tunefs - tune up an existing file systemSYNOPSIS
/usr/etc/tunefs tuneup-options special|filesysDESCRIPTION
Tunefs is designed to change the dynamic parameters of a
file system which affect the layout policies. The parame-
ters which are to be changed are indicated by the flags
given below: -a maxcontig
This specifies the maximum number of contiguous blocks
that will be laid out before forcing a rotational delay
(see -d below). The default value is one, since most
device drivers require an interrupt per disk transfer.
Device drivers that can chain several buffers together
in a single transfer should set this to the maximum
chain length. -d rotdelay
This specifies the expected time (in milliseconds) to
service a transfer completion interrupt and initiate a
new transfer on the same disk. It is used to decide
how much rotational spacing to place between successive
blocks in a file. -e maxbpg
This indicates the maximum number of blocks any single
file can allocate out of a cylinder group before it is
forced to begin allocating blocks from another cylinder
group. Typically this value is set to about one quar-
ter of the total blocks in a cylinder group. The
intent is to prevent any single file from using up all
the blocks in a single cylinder group, thus degrading
access times for all files subsequently allocated in
that cylinder group. The effect of this limit is to
cause big files to do long seeks more frequently than
if they were allowed to allocate all the blocks in a
cylinder group before seeking elsewhere. For file sys-
tems with exclusively large files, this parameter
should be set higher. -m minfree
This value specifies the percentage of space held back
from normal users; the minimum free space threshold.
The default value used is 10%. This value can be set
to zero, however up to a factor of three in throughput
will be lost over the performance obtained at a 10%
threshold. Note that if the value is raised above the
current usage level, users will be unable to allocate
files until enough files have been deleted to get under
the higher threshold. -o optimization preference
The file system can either try to minimize the time
spent allocating blocks, or it can attempt minimize the
space fragmentation on the disk. If the value of
minfree (see above) is less than 10%, then the file
system should optimize for space to avoid running out
of full sized blocks. For values of minfree greater
than or equal to 10%, fragmentation is unlikely to be
problematical, and the file system can be optimized for
time.SEE ALSO
fs(5), newfs(8), mkfs(8) M. McKusick, W. Joy, S. Leffler, R. Fabry, ``A Fast File
System for UNIX'', ACM Transactions on Computer Systems 2,
3. pp 181-197, August 1984. (reprinted in the System
Manager's Manual, SMM:14)BUGS
This program should work on mounted and active file systems.
Because the super-block is not kept in the buffer cache, the
changes will only take effect if the program is run on
dismounted file systems. To change the root file system,
the system must be rebooted after the file system is tuned.You can tune a file system, but you can't tune a fish.
% .
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