Ext3 users - Nov 2001 - Reading output from "debugfs -R stat <8>"

Hi,

I'm trying to understand if my journal is fragmented.  Here's some
output
from `debugfs -R "stat <8>" /dev/sda3`:
Inode: 8   Type: regular    Mode:  0600   Flags: 0x0   Generation: 0
User:     0   Group:     0   Size: 104857600
File ACL: 0    Directory ACL: 0
Links: 1   Blockcount: 205016
Fragment:  Address: 0    Number: 0    Size: 0
ctime: 0x3c0442fd -- Tue Nov 27 17:50:53 2001
atime: 0x00000000 -- Wed Dec 31 16:00:00 1969
mtime: 0x3c0442fd -- Tue Nov 27 17:50:53 2001
BLOCKS:
(0-11):506-517, (IND):518, (12-1035):519-1542, (DIND):1543, (IND):1544,
(1036-2059):1545-2568, (IND):2569, (2060-3083):2570-3593, (IND):3594,
(3084-4107):3595-4618, (IND):4619, (4108-5131):4620-5643, (IND):5644,
(5132-6155):5645-6668, (IND):6669, (6156-7179):6670-7693, (IND):7694,
(7180-8203):7695-8718, (IND):8719, (8204-9227):8720-9743, (IND):9744,
(9228-10251):9745-10768, (IND):10769, (10252-11275):10770-11793, (IND):11794,
(11276-12299):11795-12818, (IND):12819, (12300-13323):12820-13843, (IND):13844,
(13324-14347):13845-14868, (IND):14869, (14348-15371):14870-15893, (IND):15894,
(15372-16395):15895-16918, (IND):16919, (16396-17419):16920-17943, (IND):17944,
(17420-18443):17945-18968, (IND):18969, (18444-19467):18970-19993, (IND):19994,
(19468-20491):19995-21018, (IND):21019, (20492-21515):21020-22043, (IND):22044,
(21516-22539):22045-23068, (IND):23069, (22540-23563):23070-24093, (IND):24094,
(23564-24587):24095-25118, (IND):25119, (24588-25600):25120-26132
TOTAL: 25627

=====
This is on a new ext3 FS created with `mke2fs -J size=100 /dev/sda3`.

I understand the concept of inderect blocks, and double inderect blocks, but
I don't understand the output given by this command.  Some of the numbers in
() overlap numbers that are not in ().  Can someone explain, or point me to
a manual that I can read?

Since "Group 0" is the first and "Group 30" is the last
block
group, does that mean that they *are* contiguous?

debugfs -R "stats" /dev/sda3:
Filesystem volume name:   <none>
Last mounted on:          <not available>
Filesystem UUID:          c7577696-3fae-4379-9539-586e88779e7f
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      has_journal filetype sparse_super
Filesystem state:         clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              493024
Block count:              985989
Reserved block count:     49299
Free blocks:              944872
Free inodes:              493013
First block:              0
Block size:               4096
Fragment size:            4096
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         15904
Inode blocks per group:   497
Last mount time:          Wed Dec 31 16:00:00 1969
Last write time:          Tue Nov 27 17:50:53 2001
Mount count:              0
Maximum mount count:      23
Last checked:             Tue Nov 27 17:50:47 2001
Check interval:           15552000 (6 months)
Next check after:         Sun May 26 18:50:47 2002
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:		  128
Journal UUID:             <none>
Journal inode:            8
Journal device:	          0x0000
First orphan inode:       0
 Group  0: block bitmap at 2, inode bitmap at 3, inode table at 4
           6635 free blocks, 15893 free inodes, 2 used directories
 Group 30: block bitmap at 983040, inode bitmap at 983041, inode table at 983044
           2450 free blocks, 15904 free inodes, 0 used directories

The rest of the groups average out to:
 Group  1: block bitmap at 32770, inode bitmap at 32771, inode table at 32772
           32267 free blocks, 15904 free inodes, 0 used directories

Mike Fedyk wrote:
> 
> (0-11):506-517, (IND):518, (12-1035):519-1542, (DIND):1543, (IND):1544,
(1036-2059):1545-2568, (IND):2569, (2060-3083):2570-3593, (IND):3594,
(3084-4107):3595-4618, (IND):4619, (4108-5131):4620-5643, (IND):5644,
(5132-6155):5645-6668, (IND):6669, (6156-7179):6670-7693, (IND):7694,
(7180-8203):7695-8718, (IND):8719, (8204-9227):8720-9743, (IND):9744,
(9228-10251):9745-10768, (IND):10769, (10252-11275):10770-11793, (IND):11794,
(11276-12299):11795-12818, (IND):12819, (12300-13323):12820-13843, (IND):13844,
(13324-14347):13845-14868, (IND):14869, (14348-15371):14870-15893, (IND):15894,
(15372-16395):15895-16918, (IND):16919, (16396-17419):16920-17943, (IND):17944,
(17420-18443):17945-18968, (IND):18969, (18444-19467):18970-19993, (IND):19994,
(19468-20491):19995-21018, (IND):21019, (20492-21515):21020-22043, (IND):22044,
(21516-22539):22045-23068, (IND):23069, (22540-23563):23070-24093, (IND):24094,
(23564-24587):24095-25118, (IND):25119, (24588-25600):25120-26132
> TOTAL: 25627
Yup.  That's a perfect unfragmented file.
 
> 
> I understand the concept of inderect blocks, and double inderect blocks,
but
> I don't understand the output given by this command.  Some of the
numbers in
> () overlap numbers that are not in ().  Can someone explain, or point me to
> a manual that I can read?
The numbers in parentheses are the logical block numbers - the
offset into the file. The unparenthesised numbers are physical block
numbers, relative to the start of the disk partition.  So the table
is showing the logical->physical mapping for a single file.
 
> The rest of the groups average out to:
>  Group  1: block bitmap at 32770, inode bitmap at 32771, inode table at
32772
>            32267 free blocks, 15904 free inodes, 0 used directories
A block group is that number of blocks which can be managed
with a block's worth of bits in the bitmap.  I think.

So with 4k blocksize, the bitmap block has 32k bits.  So the
block group has 32k blocks.  That's 128 megabytes.

So your disk is approx 30 * 128 megabytes, I trust.  The 30 block
groups are spread evenly and linearly across the partition.