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Old 12-28-2011, 01:42 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

Last week the SSD in my laptop threw errors when I was doing a backup
copy of it. Only 69 of 70 GB copied using Dolphin disk to disk with
"Auto Skip" enabled when there were errors. I guess the good part is
that 69 of 70 GB of data copied during the backup and the other good
part is that I store my most essential data on another drive. So
maybe not much was lost, although the copy was my home directory, so
the data lost has to be of some importance.

You can read about the initial experience in the thread "File copy
errors on EXT4 SSD but fsck says its clean ????" on this list.

I'd like to take a kick at the cat at restoring the rest of my data
and determining what happened.

I ran the BIOS tools on both the memory (RAM) and the hard drive
itself on the laptop. Both tools returned no errors, as did all the
other tools that I have run against this drive. (See previous
thread.)

I am attempting to mount the drive via a USB external drive interface
on another machine. When I connect the interface, dmesg gives me
this:

usb 2-1.2: new high speed USB device number 4 using ehci_hcd
[ 142.896505] usb 2-1.2: New USB device found, idVendor=152d, idProduct=2338
[ 142.896508] usb 2-1.2: New USB device strings: Mfr=1, Product=2,
SerialNumber=5
[ 142.896509] usb 2-1.2: Product: USB to ATA/ATAPI Bridge
[ 142.896511] usb 2-1.2: Manufacturer: JMicron
[ 142.896512] usb 2-1.2: SerialNumber: C609942002B8
[ 142.897806] scsi9 : usb-storage 2-1.2:1.0
[ 143.897825] scsi 9:0:0:0: Direct-Access INTEL SS DSA2M160G2GC
02G9 PQ: 0 ANSI: 2 CCS
[ 143.898332] sd 9:0:0:0: Attached scsi generic sg2 type 0
[ 143.898919] sd 9:0:0:0: [sdb] 312581808 512-byte logical blocks:
(160 GB/149 GiB)
[ 143.899642] sd 9:0:0:0: [sdb] Write Protect is off
[ 143.899644] sd 9:0:0:0: [sdb] Mode Sense: 00 38 00 00
[ 143.900408] sd 9:0:0:0: [sdb] Asking for cache data failed
[ 143.900411] sd 9:0:0:0: [sdb] Assuming drive cache: write through
[ 143.902663] sd 9:0:0:0: [sdb] Asking for cache data failed
[ 143.902665] sd 9:0:0:0: [sdb] Assuming drive cache: write through
[ 143.903904] sdb: unknown partition table
[ 143.906419] sd 9:0:0:0: [sdb] Asking for cache data failed
[ 143.906421] sd 9:0:0:0: [sdb] Assuming drive cache: write through
[ 143.906423] sd 9:0:0:0: [sdb] Attached SCSI disk

What should I do now ?
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Old 12-28-2011, 01:44 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or
OSF disklabel
Building a new DOS disklabel with disk identifier 0xf7941c52.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): p

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xf7941c52

Device Boot Start End Blocks Id System
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Old 12-28-2011, 01:50 AM
Sam Varshavchik
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

linux guy writes:


# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or
OSF disklabel
Building a new DOS disklabel with disk identifier 0xf7941c52.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by
w(rite)


Command (m for help): p

Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xf7941c52

Device Boot Start End Blocks Id System


Looks like the partition table took a hit. Unless you remember your
partition layout, you're pretty much done. The only thing you can do is
create a new partition table, format them, and make a fresh start.


But, at this point, I wouldn't trust the drive.

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Old 12-28-2011, 02:02 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

Is there any way to sniff out the old partition table ? What would
I need other than the partition table sizes ? I know I had boot,
swap and / partitions...

Is there any way to copy (and possibly recover) the raw data from the
drive ? Possibly using dd or something ?

I tried using partimage, but as you guys know, if there is no
partition (partition table), it can't copy it.

What are the chances that if I could recover the partition table that
the data would still be there ?

Aside: this caught me TOTALLY off guard. SMART was enabled for this
drive, the drive was checked periodically, etc. This laptop hadn't
moved off my desk in months and was basically only rebooted to run
newer kernels.

I did my last backup about a month ago. I have a backup of all my
emails, so that is good. All my digital images are stored on a
separate drive, so none of them were lost. I'm trying to figure out
what content I added in the last month... documents, etc, that got
stored in /home/me. I shudder at the thought of sorting this all
out.
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Old 12-28-2011, 02:03 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

What are the chances that the drive controller in the laptop caused
this problem ?

I just tested the drive in the laptop BIOS and it says its fine.
SMART and what it does for a surface scan.
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Old 12-28-2011, 02:09 AM
fred smith
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

On Tue, Dec 27, 2011 at 08:02:07PM -0700, linux guy wrote:
> Is there any way to sniff out the old partition table ? What would
> I need other than the partition table sizes ? I know I had boot,
> swap and / partitions...

FYI:

A year or so ago I had a USB HD with 200-300 gigs of irreplaceable
data on it, formatted as (iirc) ext3. then I accidentally (some
might say "stupidly") did a DOS format on the drive. MAJOR OOPS.

I tried some free tools to recover files, and didn't find them very
helpful (one of 'em saved bazillions of files with no useful filenames).

googling around I found a company doing business in INdia selling
software that will recover windows/dos/mac/linux filesystems, and can
run on windows or linux. not finding anything else promising, I sprung
for the 50 bucks.

the software is somewhat flaky, isn't necessarily trivial to use,
some of the options don't work in intuitive ways. but to shorten this
long story, I managed to recover pretty much everything that was on
the drive, after banging on it for a few days.

I had some questions about how to use the software that I sent
via email to their support email address, a couple of times, and have
yet to receive any response from them, so it's clearly a case of
caveat emptor.

As best as I can remember, it was called "Recover Data for Linux".

So, if you've got a hosed partition table, you may be in a similar
position to what I was in, so maybe, just maybe, it would be helpful
for you.

YMMV! I'm not providing any warranties.


>
> Is there any way to copy (and possibly recover) the raw data from the
> drive ? Possibly using dd or something ?
>
> I tried using partimage, but as you guys know, if there is no
> partition (partition table), it can't copy it.
>
> What are the chances that if I could recover the partition table that
> the data would still be there ?
>
> Aside: this caught me TOTALLY off guard. SMART was enabled for this
> drive, the drive was checked periodically, etc. This laptop hadn't
> moved off my desk in months and was basically only rebooted to run
> newer kernels.
>
> I did my last backup about a month ago. I have a backup of all my
> emails, so that is good. All my digital images are stored on a
> separate drive, so none of them were lost. I'm trying to figure out
> what content I added in the last month... documents, etc, that got
> stored in /home/me. I shudder at the thought of sorting this all
> out.
> --
> users mailing list
> users@lists.fedoraproject.org
> To unsubscribe or change subscription options:
> https://admin.fedoraproject.org/mailman/listinfo/users
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> Have a question? Ask away: http://ask.fedoraproject.org

--
---- Fred Smith -- fredex@fcshome.stoneham.ma.us -----------------------------
The Lord is like a strong tower.
Those who do what is right can run to him for safety.
--------------------------- Proverbs 18:10 (niv) -----------------------------
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Old 12-28-2011, 02:13 AM
Craig White
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

On Tue, 2011-12-27 at 20:03 -0700, linux guy wrote:
> What are the chances that the drive controller in the laptop caused
> this problem ?
>
> I just tested the drive in the laptop BIOS and it says its fine.
> SMART and what it does for a surface scan.
----
definitely possible - might be useful to see if you can connect it to a
different computer with a different interface - there's many little USB
to notebook (2.5 in) SATA drives available.

Craig


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Old 12-28-2011, 02:15 AM
Sam Varshavchik
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

linux guy writes:


What are the chances that the drive controller in the laptop caused
this problem ?

I just tested the drive in the laptop BIOS and it says its fine.
SMART and what it does for a surface scan.


Yes, I'm sure it's fine now. Looks to me like some pages went bad, and the
drive mapped them out and replaced with some spare pages held in reserve.
Unfortunately, the bad pages were mapped to the initial sectors that held
the partition table and the bootloader.


The partition table is stored only in one place. There's no backup copy of
it. I suppose that it's theoretically possible to scan the sectors looking
for something that looks like the start of an ext4 partition. It'll probably
be on sector 63 or 2048, and from the ext4 superblock figure out the
partition's size, then past it scan for the next partition's ext4
superblock, and be able to reconstruct the partition table that way. But I
don't know of any tool that would do that.


In this respect, I say that SSDs are no better than mechnical drives. For
peace of mind, nothing beats a pair of RAID-1 drives. One drive goes bad –
it's easy to swap it out without losing any data.


Plus, when you have one of those once-in-a-biennial events like the old
100mb for /boot not being big enough any more, or grub growing too fat to
fit within the first 63 sectors, with RAID-1 you'll be able to sweat it out,
and survive, without having to wipe everything and fresh-install from
scratch.


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Old 12-28-2011, 02:18 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

On Tue, Dec 27, 2011 at 8:13 PM, Craig White <craigwhite@azapple.com> wrote:
> definitely possible - might be useful to see if you can connect it to a
> different computer with a different interface

I've done that. Its now connected to a server that I'm using for my
desktop machine via a USB interface. That is how I got the dmesg
output.

Thanks
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Old 12-28-2011, 02:19 AM
linux guy
 
Default Recovering a failed (SSD) hard drive. Unknown partition type.

On Tue, Dec 27, 2011 at 8:09 PM, fred smith
<fredex@fcshome.stoneham.ma.us> wrote:
<snip>

Thanks for sharing that, Fred. I just spent some time going through
the files that did copy and I can't see anything critical missing.
:HUGE, HUGE sigh of relief. If the situation were worse, I'd be on
your suggestion like white on <white> rice.

Thanks for the reply.
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