RT-11 Drive Partitions

[David Coolbear]

OK, I almost hate to ask the question, because it's probably obvious, but,
how does one create and format partitions on a drive in RT-11? If you do
a 'show devices' then it seems to indicate that the DU device can have
multiple partitions, but I'm wondering how to create them.

[Jerome H. Fine]

Post by David Coolbear
OK, I almost hate to ask the question, because it's probably obvious, but,
how does one create and format partitions on a drive in RT-11? If you do
a 'show devices' then it seems to indicate that the DU device can have
multiple partitions, but I'm wondering how to create them.

Jerome Fine replies:

FIRST, understand that in the DEC world with a PDP-11,
FORMAT is very different from the Windows world where
FORMAT includes the setting of of the file structure of a device.

With a PDP-11 in general and RT-11 in particular, FORMAT
is ONLY (except for a few exceptions with 8" floppy media)
with respect to the LLF (low level format) of a complete device.

INITIALIZE in RT-11 is used to set up the file structure of a
device after RT-11 is running. So it is necessary to have at least
one working RT-11 device to INIT a second device or RT-11
partition.

Each RT-11 partition is exactly 65536 blocks long except for the
last RT-11 partition on the device which uses what is left of the
device. RT-11 currently supports up to 256 partitions on a
device which is 8 GBytes or 256 * 65536 blocks.

If you are using a large SCSI drive with the DU(X).SYS device
driver, then you first set up a map entry via:
SET DUn: PORT=c, UNIT=u, PART=p
for standard DEC distributed monitors after V05.03 of RT-11.
n = logical unit number ( 0 <=n <= 7)
c = controller number (0 <= c <= 3)
u = physical unit number (0 <= u <= 255)
p = partition number (0 <= p <= 255)

Starting with V05.06 of RT-11, DEC finally added the one
missing instruction to the boot program which allowed DUP.SAV
to boot NON-ZERO partitions.

If you have a non-DEC controller which supports partitions
so that you seem to have multiple UNIT numbers for each
physical hard drive, then it is possible to have separate unit
numbers for RT-11. But, if any portion of the hard drive is
already has a FORMAT, then all of the hard drive has a FORMAT
and ONLY an INIT is needed to use the other UNITs under
RT-11.

Sincerely yours,

Jerome Fine
--
To obtain the original e-mail address, please remove
the ten characters which immediately follow the 'at'.
If you attempted to send a reply and the original e-mail
address has been discontinued due a high volume of junk
e-mail, then the semi-permanent e-mail address can be
obtained by replacing the four characters preceding the
'at' with the four digits of the current year.

[W"dot"Williams]

Is "LD" (Logical Disk Formatting Program) used to define these
"partitions" in these circumstances?

See Chapter 9 of
http://www.computer.museum.uq.edu.au/RT-11/AA-M239B-TC%20RT-11%20System%20Utilities%20Manual.tif
(mind the long URL!)

Wilber

Post by Jerome H. Fine

Post by David Coolbear
OK, I almost hate to ask the question, because it's probably obvious, but,
how does one create and format partitions on a drive in RT-11? If you do
a 'show devices' then it seems to indicate that the DU device can have
multiple partitions, but I'm wondering how to create them.

FIRST, understand that in the DEC world with a PDP-11,
FORMAT is very different from the Windows world where
FORMAT includes the setting of of the file structure of a device.
With a PDP-11 in general and RT-11 in particular, FORMAT
is ONLY (except for a few exceptions with 8" floppy media)
with respect to the LLF (low level format) of a complete device.
INITIALIZE in RT-11 is used to set up the file structure of a
device after RT-11 is running. So it is necessary to have at least
one working RT-11 device to INIT a second device or RT-11
partition.
Each RT-11 partition is exactly 65536 blocks long except for the
last RT-11 partition on the device which uses what is left of the
device. RT-11 currently supports up to 256 partitions on a
device which is 8 GBytes or 256 * 65536 blocks.
If you are using a large SCSI drive with the DU(X).SYS device
SET DUn: PORT=c, UNIT=u, PART=p
for standard DEC distributed monitors after V05.03 of RT-11.
n = logical unit number ( 0 <=n <= 7)
c = controller number (0 <= c <= 3)
u = physical unit number (0 <= u <= 255)
p = partition number (0 <= p <= 255)
Starting with V05.06 of RT-11, DEC finally added the one
missing instruction to the boot program which allowed DUP.SAV
to boot NON-ZERO partitions.
If you have a non-DEC controller which supports partitions
so that you seem to have multiple UNIT numbers for each
physical hard drive, then it is possible to have separate unit
numbers for RT-11. But, if any portion of the hard drive is
already has a FORMAT, then all of the hard drive has a FORMAT
and ONLY an INIT is needed to use the other UNITs under
RT-11.
Sincerely yours,
Jerome Fine
--
To obtain the original e-mail address, please remove
the ten characters which immediately follow the 'at'.
If you attempted to send a reply and the original e-mail
address has been discontinued due a high volume of junk
e-mail, then the semi-permanent e-mail address can be
obtained by replacing the four characters preceding the
'at' with the four digits of the current year.

[Carl Lowenstein]

Post by W"dot"Williams
Is "LD" (Logical Disk Formatting Program) used to define these
"partitions" in these circumstances?

LD allows you to use a file on a larger disk drive as an image of
a (smaller) drive. This makes it possible to set up a somewhat
limited hierarchical file system on RT11, which was frequently useful.

I would frequently have several 4800-block (RK05-size) disk images
stored on a 32MB partition of a larger drive. In that way, the
particular focus of interest for the day could be mounted and even
assigned to the default device DK. Other projects would be out of
the way. This also saves on user's short-term memory, since directory
listings are much shorter.

carl

[Ed Kelleher]

Post by W"dot"Williams
Is "LD" (Logical Disk Formatting Program) used to define these
"partitions" in these circumstances?

! for an ST251 (RD32) 40MB drive, DU0: uses 32mb
! to use the remainder:

Set DU4: Unit=0, part=1

! for the change to take effet
! If DU is your system disk, reboot
! if not, reload the device handler:

unl du:
rem du:
ins du:
loa du:

! init the new partition, you'll have 17,600 free blocks

ini du4:

! make a sub disk file on the partition
!

cre du4:bigone.dsk[5000]
cre du4:bigtwo.dsk[-1] ! [-1] means use largest free space
mou ld0 du4:bigone.dsk
mou ld1 du4:bigtwo.dsk
ini ld0:
ini ld1:
dir ld0:
dir ld1:

!
! Logical Disks default to 4 directory segments
! for lots of little files you may want more

ini/seg:30 ld1:

show sub ! to show which logical disks (sub-disks) are mounted

dismou ld0: ! remove the logical disk

set ld0 empty ! remove all logical disk assignments