copying large files between filesystems
Mike Fedyk
mfedyk at matchmail.com
Wed Jun 30 23:08:04 UTC 2004
Andrew Scott wrote:
> Good advice. The disk isn't currenlty mounted and I'm running badblocks
> on it in read-only mode writing the output to a file. Interesting side
> note: the output file has been created but no bad blocks show up in it
> yet -- does badblocks only write on exit to the output file? Otherwise,
> perhaps it's just the drive controller or the SCSI card that are
> throwing errors and the data is safe and sound (oh, I hope this is true).
Ahh, you're using scsi?
Can you post excerpts from your kernel logs?
>> Yeah, run
>>
>> hdparm -d0 /dev/drive
>>
>
> Excellent idea. I'll do this once badblocks finishes (looks like
> another hour). Though hdparm /dev/sda doesn't really return much along
> the lines of configurable options, I'll have to try this none-the-less.
> Thanks.
Sorry, this won't help with scsi... :(
>> and then:
>>
>> dd bs=1 if=your-file-to-recover of=file-on-a-different-drive
>>
>
> Also, excellent idea. I was trying to read the filesystem blocksize of
> 4K. Totally stupid, I should go bit by bit!
>
Actually byte by byte...
> I'll try these things next. Thanks for your thoughts. Excellent
> suggestions.
>
>> this will copy your file one byte at a time, creating more processing
>> overhead which will slow you down.
>>
>> Obviously, I don't know of any tools that rate limit file copying,
>> except for maybe rsync, but I'm not sure about that either.
>>
>>>
>>> I emailed the guys at Namesys (reiserfs headquarters in Oakland, CA).
>>> They have a standing offer of "Ask any questions for $25". I sent
>>> them $25 and asked them a question. Hans Reiser got back to me as
>>> well as another employee, both with good suggestions. They suspected
>>> the hardware immediately. They made one really keen suggestion: if
>>> the bit count is identical on the original as the copy (when copied
>>> to another filsystem), but the md5sums are different, then try and
>>> run bindiff on the two files and use a binary editor to toggle the
>>> differing bits, with the goal of a correct md5sum match. I imagine
>>> this will the last thing
>>
>>
>>
>> that's nice, but don't try that on the entire 2gb file, split it up
>> first...
>>
>
> Good idea but how can I tell the split up files are actually good copies?
run cmp (compare) on the two files, it will tell you where they are
different.
>>> I try before sending the disk off for disk recovery.
>>>
>>> Anyway, thanks a lot for your time and thoughts. What a pain in the
>>> ass.
>>>
>>
>> Yep, anyone wonder why people like RAID?
>>
>
> Support your local student.
>
Use IDE, then people might consider that... ;)
Mike
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