raid5 data recovery and 0 bytes file size

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Expand view Topic review: raid5 data recovery and 0 bytes file size

Re: raid5 data recovery and 0 bytes file size

by Alt » Mon Jul 01, 2013 8:25 am

Quite often data recovery software shows a "correct" file system on a RAID even some parameters are wrong. That may have when its MFT is less than a block size.
What I recommend you is to use this free program: ReclaiMe Free RAID Recovery. It can find right parameters for a RAID5 even when one disk is missing. Then create a virtual RAID with those parameters and see what happens. Well, that may take really a lot of time, so be patient.

Re: raid5 data recovery and 0 bytes file size

by exequos » Sun Jun 30, 2013 8:06 am

You said that one disk is broken, what did you use in R-Studio as its substitute?
It was runtime package software - what i only was to try as I couldn't mount the vim file under captain nemo
So in general only R-Studio shows me resonable results (some files were 0bytes some more and readable with proper data)
Quite possible.
No difference except file size limitations during recovery.
My idea for this situation is that some files were uploaded to degraded volume which brokes suddenly so the files doesn't copy properly to raid strips

I've tryied different RAID5 settings with runtime nas recovery, but only one show results - in case of R-studio it was much simpler just drop and drag with the biggest partitions and checking if the virtual raid show proper volume.
What i thought maybe as a possibility was that for example settings with 4KB or 64KB block will show the some file structure and 0bytes files can have proper size.

In this case it looks rather as broken structure data than wrong reading settings yes?

Pls have a look for the NAS data recovery settings I've tried to use with NAS recovery with no results (64KB block/128sectors, left 1-2-3, partition start 3 164 805) - I have only HDD1 and HDD2 (HDD3 is missing)

Code: Select all

Testing 2 drives...
Parsing partition tables for 2 drives...
Parsing partition table for DISK1:, 2 930 277 168 sectors (1,36 TB)...
Drive DISK1: has 3 partitions
Partition #1 at sector 63, 1 060 227 sectors: Prime or Linux swap or Solaris UNIX (130) 
Partition #2 at sector 3 164 805, 2 925 532 890 sectors: Linux (131) 
Partition #3 at sector 1 060 290, 2 104 515 sectors: Linux (131) 
Parsing partition table for DISK2:, 2 930 277 168 sectors (1,36 TB)...
Drive DISK2: has 3 partitions
Partition #1 at sector 63, 1 060 227 sectors: Prime or Linux swap or Solaris UNIX (130) 
Partition #2 at sector 3 164 805, 2 925 532 890 sectors: Linux (131) 
Partition #3 at sector 1 060 290, 2 104 515 sectors: Linux (131) 
StartSector 3164805, 2925532890 sectors is possible data start on drive DISK1:
StartSector 3164805, 2925532890 sectors is possible data start on drive DISK2:
Creating RAID list...
  Testing possible start 3 164 805 (length 2 925 532 890)...
    ...for XFS superblock on DISK1:
    ...for XFS superblock on DISK2:
    ...for EXT2FS superblock on DISK1:
      ...valid EXT2FS superblock found, building RAID
        ...adding DISK1:
        ...adding DISK2:
        ...adding missing drive
Completing RAID list...
  Setting level of RAID no 0 to 5
  Finding drive order...
    Testing 6 possible drive orders with a probe size of 5 000 000 sectors, requiring 20%
      Best combination after 100096 sectors: 0,1,2 with entropy 0,1849 versus 0,2170 (17%)
      Best combination after 110080 sectors: 0,1,2 with entropy 0,1742 versus 0,2075 (19%)
      Best combination found after 120064 sectors: 0,1,2 with entropy 0,1633 versus 0,1993 (22%)
    Applying...
-------------
Raid settings
-------------
Raid level 5
3 drives
Drive 1: DISK1:
Drive 2: DISK2:
Drive 3: (n/a)
Partition start: 3 164 805
Partition length: 2 925 532 890 sectors (1,36 TB)
Volume length: 1 556 098 048 sectors (742 GB)
1 data drives are required
Stripe count: 0
Stripe size: 128 sectors
Rotation: left-symmetric
last but not least: the HDD are connected to PC in the some order as in nas (HDD1 - ch1, HDD2 - ch2 but they are not only hdd's under the controller, ch0 is system, ch3 is data)

Re: raid5 data recovery and 0 bytes file size

by Alt » Sat Jun 29, 2013 2:08 am

exequos wrote:Finally the raid partition was missing so I had to use some additional software to recover under PC.
Which software did you use and what actually have been done and what results did that yield? It's an important question to understand what's wrong with your NAS partition.

You said that one disk is broken, what did you use in R-Studio as its substitute?

I'll try to help you further when I have this information.
exequos wrote:The only problem is that the files I really need for now have size 0 Bytes.
A very bad symptom saying that the file table might be seriously corrupted.
exequos wrote:Is it possible that different configuration of RAID parition under R-studio can give better results?
Is there any difference in the file recovery between demo and registered version (the one i recognise is a limitation of file size)?
Quite possible.
No difference except file size limitations during recovery.

raid5 data recovery and 0 bytes file size

by exequos » Fri Jun 28, 2013 4:27 am

I've degraded RAID5 built on 3 HDDs (1,5TB Seagate ST31500341AS) formated in ext3 filesystem and working under DNS-343

One HDD become unstable and broken, and the RAID degraded.
The notification didn't came on time so some files become copied into raid which works in degraded state.

Finally the raid partition was missing so I had to use some additional software to recover under PC.

The R-studio works fine (With the settings which worked in R-studio I couldn't generate proper vlm file in NAS Recovery to use under Captain nemo)

I've found the data partition settings, configured in R-studio and find some files.

Some small files (like pdf txt xls) was even possible to open with demo limitation.

The only problem is that the files I really need for now have size 0 Bytes.

I've tried some other settings but only the first gives resonable results when the other ones gives exception error during file vie preparing or show not proper raid partition size.
For example I've tested changing of block size from 64KiB to other or asymetric instead of symmetric.

My questions regarding to above
Is it possible that different configuration of RAID parition under R-studio can give better results?
Is there any difference in the file recovery between demo and registered version (the one i recognise is a limitation of file size)?

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