Disk problems - hard error reading fsbn NNNNNNNN (Bullet dodged)

[Matt Navarre]

Matt Navarre wrote:

> Matt Navarre wrote:
>
>> After a power outage last night I rebooted my computer and  fsck 
>> complained of the following :
>>
>> ad1s2e: hard error reading fsbn 5103776  (ad1s2 bn 5103776; cn 317 tn 
>> 177 sn 20) status=59 error=40
>>
>> Then goes on for a while giving the same error on blocks 5103776 - 
>> 5103807, except for block 5103777 which has error=01.
>>
>> Does this mean the disk is failing, or can I just reformat? And 
>> what's the best way to recover any recoverable data from that slice? 
>> Unfortunately I don't have a recent backup, since my tape drive 
>> joined the choir invisible a while ago and I haven't had a chance to 
>> replace it.
>
>
> I seem to have recovered all the data from the failing disk, just for 
> posterity here's what worked for me.
>
> First you need two things: A new hard disk and a FreeSBIE CD. Install 
> the new harddisk and boot from the FreeSBIE cd. Then you need to make 
> a filesystem on the new disk (see the Handbook for the Magic Spells, 
> there's no /stand/sysinstall on the FreeSBIE cd). Mount the new disk. 
> If your damaged drive has data on other slices that don't have errors 
> mount them and recover the data. I used  cd /mnt/ufs.2; find ./ -xdev 
> -print0 | cpio -pa0V /mnt/ufs.1/gooddata.
>
> Now, on to the damaged sectors, how to recover the data? dd stops when 
> it hits bad blocks, so we can't use that to copy the slice. same with 
> dump(8) as far as I can tell. So. Download dd_rescue from
> http://www.garlof.de/kurt/linux/ddrescue/
>
> Version 1.10 compiled and worked out of the box. No need to install 
> it, just run it from the build folder:
>
> ./dd_rescue /dev/ad1s2e /mnt/ufs.1/ad1s2e.img
>
> Wait. a long time. keep in mind that the slice you are writing to 
> needs to be big enough to hold an image of the *entire* slice you are 
> copying.
>
> once dd_rescue finishes we're left with a (hopefully) usable image of 
> the bad slice. Now we need to use it.
>
> see the handbook entry on Network, Memory and File-Backed File systems:
> http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/disks-virtual.html 
>
>
> Here's the basic quick and dirty:
> mdonfig -a -t vnode -f /mnt/ufs.1/ad1s2e.img -u 6 #change 6 to an 
> unused /mnt/md#, freesbie mounts it's filesystems on md[0-5] on my cd.
> fsck_ffs /dev/md6
> mount /dev/md6 /mnt/ufs.3
>
> Now you should be able to get the data off the image and on to a real 
> filesystem. You can check your data with ls -lR > ls.out on the image 
> and the directory where your now hopefully rescued data is and diffing 
> the output. I saw differences in dates on directories, so if that's a 
> concern there's probably a better way to move the data than find/cpio.
>
> Now I need to come up with a real backup scheme. This one has 
> proved.... suboptimal.
>
I forgot: Keep in mind that FreeBSD 5.x defaults to UFS2 and the 
downloadable FreeSBIE isos are 5.x. If your existing system is 4.X you 
won't be able to read the drive unless you give newfs(8) the -O 1 flag.

> Matt
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