Cylinders Per Group

From: <dancing-bear_at_earthling.net>
Date: Mon, 02 Nov 1998 15:11:22 -0500 (EST)

Hello,

What does the cpg (cylinders per group) field in a disk label do?

The original factory written label had value of 12 cylinders per group
for the 'c' partition. I used the same value for other partitions
when I repartitioned the drive.

But when I make a filesystem I get the following warnings:

# /usr/sbin/newfs /dev/rrz18f
Warning: /dev/rrz18f is marked in use for 4.2BSD in the disklabel.
If you continue with the operation you can
possibly destroy existing data.
CONTINUE? [y/n] y
Warning: Block size restricts cylinders per group to 12.
Warning: 1460 sector(s) in last cylinder unallocated
/dev/rrz18f: 11796480 sectors in 1793 cylinders of 28 tracks, 235 sectors
        5760.0MB in 150 cyl groups (12 c/g, 38.55MB/g, 9216 i/g)
super-block backups (for fsck -b #) at:
 32, 79232, 158432, 237632, 316832, 396032, 475232, 554432, ...
 11374112, 11453312, 11532512, 11611712, 11690912, 11770112,

(The man page for newfs says the 'sectors unallocated' warning
requires no user action and doesn't mean space is being wasted.)
 
So I am wondering if I should change the cpg parameter in the label
and make a new filesystem.

Any advice would be greatly appreciated.

Thanks,

dancing-bear_at_earthling.net

PS: Below find the new partition table and the full original label.

----- New Partition Table -----

8 partitions:
# size offset fstype [fsize bsize cpg]
  a: 131072 0 4.2BSD 1024 8192 12 # (Cyl. 0 - 19*)
  b: 786432 131072 swap # (Cyl. 19*- 139*)
  c: 45322644 0 unused 0 0 # (Cyl. 0 - 6887*)
  d: 7864320 917504 4.2BSD 1024 8192 12 # (Cyl. 139*- 1334*)
  e: 11796480 8781824 4.2BSD 1024 8192 12 # (Cyl. 1334*- 3127*)
  f: 11796480 20578304 4.2BSD 1024 8192 12 # (Cyl. 3127*- 4920*)
  g: 8388608 32374784 4.2BSD 1024 8192 12 # (Cyl. 4920*- 6195*)
  h: 4559252 40763392 4.2BSD 1024 8192 12 # (Cyl. 6195*- 6887*)

----- Original Label -----
# /dev/rrz18c:
type: SCSI
disk: ST423451
label:
flags: dynamic_geometry
bytes/sector: 512
sectors/track: 235
tracks/cylinder: 28
sectors/cylinder: 6580
cylinders: 6876
sectors/unit: 45322644
rpm: 5400
interleave: 1
trackskew: 20
cylinderskew: 65
headswitch: 0 # milliseconds
track-to-track seek: 0 # milliseconds
drivedata: 0

8 partitions:
# size offset fstype [fsize bsize cpg]
  a: 131072 0 unused 1024 8192 # (Cyl. 0 - 19*)
  b: 262144 131072 unused 0 0 # (Cyl. 19*- 59*)
  c: 45322644 0 4.2BSD 1024 8192 12 # (Cyl. 0 - 6887*)
  d: 0 0 unused 0 0 # (Cyl. 0 - -1)
  e: 0 0 unused 0 0 # (Cyl. 0 - -1)
  f: 0 0 unused 0 0 # (Cyl. 0 - -1)
  g: 22464714 393216 unused 0 0 # (Cyl. 59*- 3473*)
  h: 22464714 22857930 unused 0 0 # (Cyl. 3473*- 6887*)
----------


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Received on Mon Nov 02 1998 - 20:12:19 NZDT

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