Just Give Me the Beans!
hi
this image from gparted shows the first sector and last sector of the partition i want to recover.
how can i translate those numbers into ddrescue parameters -s and -i? do i need to divide by 8 (a byte) or by 512 (sector size)?
thx!
gparted2.png
ddrescue.png
Last edited by johny why; March 22nd, 2015 at 12:54 PM.
A Carafe of Ubuntu
good question. answer (from man ddrescue): <in bytes>
whereas parted gives sectors, which used to be 512 bytes in the old days, more and more advances format drives are in use, where a sector has 4096 bytes. so no dividing... more like multiplier necessary
As a side note: since you are comfortable using RAID, why not make the output file sparse?
Last edited by bardo2; March 23rd, 2015 at 10:46 PM.
A Carafe of Ubuntu
Sorry, i missed to answer your question: just use the partition (sda4) instead of the whole disk as input to ddrescue. In linux, everything is seen as a file, even those block devices can be regarded as being files.
Just Give Me the Beans!
tried already, didn't work. i think the partition is too damaged. Plz see the gparted screenshot in the OP.Originally Posted by bardo2
that's exactly why i want to enter the specific locations using ddrescue start-position option.
Last edited by johny why; March 24th, 2015 at 01:10 AM.
Just Give Me the Beans!
my drive is 512 sector size. Therefor, 512 x 2721792 = 1393557504
and for the ddrescue -s option: 512 x 580456448 = 297193701376
If the above is correct, we'd do:
ddrescue -i 1393557504 -s 297193701376 /dev/sda /mnt/sdc1/recovered.img /mnt/sdc1/recovered.log
Is -s the correct parameter to specify input size? The ddrescue manual says "Maximum size of the rescue domain, in bytes. It limits the amount of input data to be copied." So i'm not sure if that means number of bytes to TRY to copy, or number of bytes to ACTUALLY copy (minus the bad data that could not be copied).
My understanding of ddrescue -S sparse is that it skips contiguous 0's, to avoid loading the output file with empty data. I understand RAID to be a scheme for preventing data-loss, by combining multiple hard-disks. Is that correct? How is 'sparse' related to RAID?As a side note: since you are comfortable using RAID, why not make the output file sparse?
thx!
Ubuntu addict and loving it
Hi, here is a nice link to tips and tricks with dd rescue.
http://www.linuxquestions.org/questi...ommand-362506/
have fun !
Craving anchovy, herring and squid pizza.....with clam sauce
A Carafe of Ubuntu
It isn't. (Sorry, still new in here and learning my ways, missed your reply.)
I am using RAID myself and consider that to be somewhat advanced technology, just as understanding sparse files. Here, i use zfs, which has raidz & compression, just saving space while copying huge amounts of data. And you are hinting to be an experienced user - to say the least - . Could i "help" someone like you? - I guess not much.
My conclusion was: there may not be a need to preserve each and every byte from ddrescue, depending on the input of course.
Yup, but damaged drives are a pain, been there myself. And ddrescue would have been my choice as well.
Last edited by bardo2; March 24th, 2015 at 02:40 AM.
Just Give Me the Beans!
That's not the same command. Thx anyway.
Just Give Me the Beans!
thx for information, tho' not related to my OP.
i'm not 'advanced'. I do not know the answer to the question in my OP-- just trying to solve that!
i appreciate any info about my question-- unrelated stuff just confuses me!
thx
A Carafe of Ubuntu
If I understand what u r trying to do (and I apologise in advance if I dont)
then
the command above will not limit the size of the image file to exactly that of your partition. In other words, the image file will not be the same as using /dev/sda4. It will be bigger.
To put it another way, this (hilite is the difference in the two commands):
ddrescue -i 1393557504 -s 297193701376 /dev/sda /mnt/sdc1/recovered.img /mnt/sdc1/recovered.log
will not give you the same image file as this:
ddrescue /dev/sda4 /mnt/sdc1/recovered.img /mnt/sdc1/recovered.log
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