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Re: [Bug-ddrescue] backingup a drive as a disk image onto a drive/array
DePriest, Jason R.
Re: [Bug-ddrescue] backingup a drive as a disk image onto a drive/array already in use
Tue, 24 Jul 2007 17:05:22 -0500
On 7/24/07, stephbal1wrote:
Please accept my apologies for sending this email to the 'Bug-ddrescue' mailing
list as I am asking for help and not reporting any bug. Disk failure is new to
me and after days of searching through maunuals and forums I am still not sure
my intended use of ddrescue is correct. Any help would be highly appreciated.
The PC my daily work relies upon has the following set up:
- unit 0, /dev/sda: a drive with the OS on, opensuse 10.0, with a size of
290GB, and 18GB used.
- unit 1, /dev/sdb: a RAID 10 array, for the users accounts, with a size of
~600GB, ~370GB used, and 220GB available.
The drive with unit 0 has 26 badblocks. I want to make a backup of that failing
disk, eg as in the info file for ddrescue, section 6 'direct disc access',
example 1. I do not have any new disk right now. I would therefore like the
failing disk, the input, to be backuped as a disk image on the array, the
output, without doing anything else (eg repartioning) to this array as I need
it as it is.
Here is what I would try, from the rescue boot, having mounted the array on
ddrescue -n /dev/sda /dev/sdb1/users/lab/Documents/my_os_bu.img
ddrescue -dr3 /dev/sda /dev/sdb1/users/lab/Documents/my_os_bu.img
Here are my questions:
-Q1- Will the above usage of ddrescue corrupt the array and make the situation
It will not corrupt the array. You are saving the image to a .img
file which is good.
-Q2- Will it try to copy the 290GB of unit 0 (/dev/sda) into the 220GB
available on the array (/dev/sdb1/), and therefore fill up the array and fail
to copy the OS drive entirely?
Yes. When it runs out of space, maybe even a bit before depending on
your OS, it will stop. Not a good idea as it could cause some
Can you create a compressed volume or something like that and put the
image file there temporarily?
If you are on a network, can you put a netcat listener on a system
with more space?
-Q3- To avoid this, should I rather use the -s option to tell ddrescue to stop
after 20GB for example as I want the 18GB of data and not the entire, otherwise
That wouldn't guarantee that you get the data you want.
-Q4- [How] Do I know the 18GB I want will be in these first 20GB, and not
scattered all over the drive?
You can't unless you do some sort of analysis of the disk and find out
where the data you want is physically located.
I pasted below output from 'mount', 'fdisk -l' and the /proc/partitions file.
I am stuck! Please help.
/dev/sda2 on / type reiserfs (rw,acl,user_xattr)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
tmpfs on /dev/shm type tmpfs (rw)
devpts on /dev/pts type devpts (rw,mode=0620,gid=5)
/dev/sdb1 on /local type reiserfs (rw,acl,user_xattr,usrquota,grpquota)
usbfs on /proc/bus/usb type usbfs (rw)
/dev/fd0 on /media/floppy type subfs
/dev/hda on /media/dvdrecorder type subfs
%fdisk -l /dev/sda2:
Disk /dev/sda: 319.9 GB, 319988695040 bytes
255 heads, 63 sectors/track, 38903 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 1045 8393931 82 Linux swap / Solaris
/dev/sda2 * 1046 38903 304094385 83 Linux
major minor #blocks name
8 0 312488960 sda
8 1 8393931 sda1
8 2 304094385 sda2
8 16 624977920 sdb
8 17 624968631 sdb1
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