raidtools to mdadm

raidtools to mdadm

[Casey Boone]

ok so i am trying to recover some data for a friend.  what i am wanting 
to do is forcibly set up /dev/mdN to be a raid0 of /dev/sda and /dev/sdb

i do not want to actually change any of the contents of these drives, 
just mount very simply as a raid0.  the raid was originally created 
using an onboard nvidia raid on the motherboard these drives used to be 
hooked to.  my friend thought he could shove them into another windows 
box (that is what he was running on them) and have windows recover the 
raid.  all this did was totally destroy the superblock on one of the two 
drives.  dmraid now wont see them as a matched pair so that is out.  the 
actual data areas of both drives seems to be intact, but unless i can 
get them into raid0 i dont know how i can recover the data.  it figures 
he gives me the drives after he makes it a notch or two more of a pain :\


now before the advent of mdadm i would use /etc/raidtab and have no 
issues setting up the raid device.


as best i can tell i am using the correct commands for what i want but i 
pretty much get nothing but errors:

root@Knoppix:/media# mdadm --build /dev/md1 --chunk=128 --level=0 
--raid-devices=2 /dev/sda /dev/sdb
mdadm: error opening /dev/md1: No such device or address
root@Knoppix:/media# mdadm --build -n 2 -c 128 -l 0 /dev/md1 /dev/sda 
/dev/sdb
mdadm: error opening /dev/md1: No such device or address


when i run those commands i do get /dev/mdN entries created, but they do 
not point to a valid block device (as tested with fdisk -l and with 
dmraid -b)


for the life of me i dont understand why anyone would put important data 
on a raid0, but that is what happened in this case.


If i have to i will drop down to an older knoppix release to get 
raidtools back, as i have never had any issues in recovering crap 
onboard raid arrays nor windows software raid arrays under it.  i am 
sure it can be done with mdadm but for the life of me i cannot seem to 
figure out exactly how.

any help on this would be greatly appreciated

Casey

Re: raidtools to mdadm

[Neil Brown]

On Sunday April 1, caseyboone@gmail.com wrote:
> as best i can tell i am using the correct commands for what i want but i 
> pretty much get nothing but errors:
> 
> root@Knoppix:/media# mdadm --build /dev/md1 --chunk=128 --level=0 
> --raid-devices=2 /dev/sda /dev/sdb
> mdadm: error opening /dev/md1: No such device or address

"No such device or address" probably means that the md module is not
loaded. 
  modprobe md
or
  modprobe md_mod

and try again.

NeilBrown

Re: raidtools to mdadm

[Bill Davidsen]

Casey Boone wrote:
> ok so i am trying to recover some data for a friend.  what i am 
> wanting to do is forcibly set up /dev/mdN to be a raid0 of /dev/sda 
> and /dev/sdb
>
> i do not want to actually change any of the contents of these drives, 
> just mount very simply as a raid0.  the raid was originally created 
> using an onboard nvidia raid on the motherboard these drives used to 
> be hooked to.  my friend thought he could shove them into another 
> windows box (that is what he was running on them) and have windows 
> recover the raid.  all this did was totally destroy the superblock on 
> one of the two drives.  dmraid now wont see them as a matched pair so 
> that is out.  the actual data areas of both drives seems to be intact, 
> but unless i can get them into raid0 i dont know how i can recover the 
> data.  it figures he gives me the drives after he makes it a notch or 
> two more of a pain :\
>
I have friends like that too. ;-)

>
> now before the advent of mdadm i would use /etc/raidtab and have no 
> issues setting up the raid device. \

I haven't used raidtools for ages, but can't you bring yourself to using 
them now? I seem to remember that there was no superblock to be written 
in a bad place, which might be an advantage. mdadm has several versions 
which write the superblock in various places on the drives, and you may 
want "none of the above."

Alternatively, if these are fairly small, write a tiny program to open 
both physical devices, read a chunk from one, then the other, repeat 
while writing to something not hosed.
>
>
> as best i can tell i am using the correct commands for what i want but 
> i pretty much get nothing but errors:
>
> root@Knoppix:/media# mdadm --build /dev/md1 --chunk=128 --level=0 
> --raid-devices=2 /dev/sda /dev/sdb
> mdadm: error opening /dev/md1: No such device or address
> root@Knoppix:/media# mdadm --build -n 2 -c 128 -l 0 /dev/md1 /dev/sda 
> /dev/sdb
> mdadm: error opening /dev/md1: No such device or address
>
>
> when i run those commands i do get /dev/mdN entries created, but they 
> do not point to a valid block device (as tested with fdisk -l and with 
> dmraid -b)
>
>
> for the life of me i dont understand why anyone would put important 
> data on a raid0, but that is what happened in this case.
>
>
> If i have to i will drop down to an older knoppix release to get 
> raidtools back, as i have never had any issues in recovering crap 
> onboard raid arrays nor windows software raid arrays under it.  i am 
> sure it can be done with mdadm but for the life of me i cannot seem to 
> figure out exactly how.
>
> any help on this would be greatly appreciated
>
> Casey 


-- 
bill davidsen <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979

Re: raidtools to mdadm

[Casey Boone]

>> i do not want to actually change any of the contents of these drives, 
>> just mount very simply as a raid0.  the raid was originally created 
>> using an onboard nvidia raid on the motherboard these drives used to 
>> be hooked to.  my friend thought he could shove them into another 
>> windows box (that is what he was running on them) and have windows 
>> recover the raid.  all this did was totally destroy the superblock on 
>> one of the two drives.  dmraid now wont see them as a matched pair so 
>> that is out.  the actual data areas of both drives seems to be 
>> intact, but unless i can get them into raid0 i dont know how i can 
>> recover the data.  it figures he gives me the drives after he makes 
>> it a notch or two more of a pain :\
>>
> I have friends like that too. ;-)
>

gotta love 'em

wish i was getting paid for this one



>>
>> now before the advent of mdadm i would use /etc/raidtab and have no 
>> issues setting up the raid device. \
>
> I haven't used raidtools for ages, but can't you bring yourself to 
> using them now? I seem to remember that there was no superblock to be 
> written in a bad place, which might be an advantage. mdadm has several 
> versions which write the superblock in various places on the drives, 
> and you may want "none of the above."
>
> Alternatively, if these are fairly small, write a tiny program to open 
> both physical devices, read a chunk from one, then the other, repeat 
> while writing to something not hosed.


at the suggestion of another on the list (thanks neil brown!) i tried 
modprobing a slew of things related to the disk mapper to no avail, then 
i gave up using knoppix and tried with a fedora 6 box (after i dd-ed the 
drives off to a larger drive) and it worked great.  i can definitely say 
that while mdadm is quite foreign territory for me, i love the fact i 
can specify everything i want to happen on one command line.

btw once i actually did get the drives raided it turns out that while 
the partition table was intact, somehow the partition itself was 
fubarred enough that i couldnt mount it to save my life.  finally just 
told the guy "you screwed it by trying to recover it, next time bring me 
the drives the MOMENT you have a problem"

Casey