1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Storage Raid array behavior, lost data?

Discussion in 'Hardware' started by yougotkicked, 30 Oct 2014.

  1. yougotkicked

    yougotkicked A.K.A. YGKtech

    Joined:
    3 Jan 2010
    Posts:
    251
    Likes Received:
    9
    So, this problem is at a bit of an intersection between hardware and software, but the source of the problem is hardware configuration so I believe this is the place to post it.

    I tend to put a lot of detail into my posts when asking for help, so if you don't want to go through everything you can skip the stuff between the DETAILS tags and you'll still get the basics of the situation.

    I have a hardware raid array (raid 1 mirroring) with two 2TB WD drives. I dual boot linux and windows from another drive. Recently my father's laptop broke down (I think the CPU failed due to a faulty fan, but the important part is that the hard drive was not effected) and we needed to send it in for warranty service, so I pulled the drive and backed it up to the raid array (I made the transfer from linux). Now windows tries to run a consistency check on the array every time I boot, and I can't access any of the files I backed up from either OS. (other files on the drive were unaffected)

    // ---- DETAILS
    For reference, the raid array is controlled by my motherboard, and the file system on it was formatted under windows. I don't usually write data to the array from linux, as I only really use linux while doing C development on a remote system.

    Prior to backing up that data, linux only ever saw the raid array as one drive, as it should with a hardware raid. Since I backed up to the array linux has been identifying the two drives separately. From what I can tell, it only wrote data to one of the drives, and a subsequent consistency check by windows has partially copied the data to the other drive (the two drive report different amounts of free space under linux, windows still sees the array as a single file system.)

    Under windows if I open the folder where I backed up, no files are shown, under linux the behavior gets a bit confusing, with slightly different behavior depending on which drive I view it from. I'll refer to the two drives as A and B, A is the drive I believe the data was copied to, since it reports less free space than B.
    I copied the entire users folder from the laptop drive into a folder on my raid array. If I open the folder on drive A with a graphical file browser, I see the Users folder, but if I open that folder no files are shown. On drive B I can't see the Users folder at all. From the command line I can see the Users folder on either drive, and calling ls from within it reports nothing but an Input/Output error.

    I have no idea why linux only wrote to one of my hard drives, as I understand it this should't happen with a hardware raid. I have enough space on my other drives that I can pull my data off of this array and rebuild it, but I'd like to know what went wrong before I do so.

    // ---- DETAILS

    My father's drive was put back in the laptop and shipped to a repair center by the time I discovered the backup was faulty, so I'm looking for a way to recover the data (unless the consistency check windows ran somehow messed things up, the data should still be there.)

    I'm still researching various aspects of the situation, but I have two ideas I'd like to get some opinions on:

    1) take the drives out of RAID (just undo the configurations in the controller menu). I think there could be a mis-communication between linux and the raid controller causing it to try and read data from both drives when data was only written to one drive. If this is the case, then I may be able to get to the data by accessing only drive A.

    2) Re-run the file system consistency check. Windows is still prompting me for a consistency check, and I think it may have only partially run the first time (I let it run once, but I can't recall if it actually completed or if it just stalled part way through. I haven't let it run since then in case it somehow damages the data more). I really don't know what this does to the drives; if someone is more familiar with what this may do please let me know.

    If anyone has any thoughts on these two idea, or any suggestions for what else I could try, I'd really appreciate it.
     
  2. play_boy_2000

    play_boy_2000 It was funny when I was 12

    Joined:
    25 Mar 2004
    Posts:
    1,495
    Likes Received:
    71
    If you have the free disk space, clone an image of each drive and then start experimenting. I'd start with letting windows do the check... I would really hope that the default behaviour is to properly duplicate the information rather than remove/damage it.
     
  3. yougotkicked

    yougotkicked A.K.A. YGKtech

    Joined:
    3 Jan 2010
    Posts:
    251
    Likes Received:
    9
    Sorry for the delayed reply, I've been a bit busy lately.

    I've not had any luck with it yet. I decided the best thing to do was to just let the consistency check run, though it didn't end up improving the situation at all. The files are now invisible on both drives when working in linux, though the drives still report different amounts of free space.

    Ultimately I'm hoping that the hard drive will be returned to us without them formatting it, since there was absolutely nothing wrong with the drive or the software configuration. I know some companies will re-install windows regardless of what the issue is, but I won't know for sure until we get the drive back.
     
  4. Guinevere

    Guinevere Mega Mom

    Joined:
    8 May 2010
    Posts:
    2,484
    Likes Received:
    176
    Here's what I would do...

    - Pull out both drives
    - Disable the RAID in the BIOS / HW config
    - Boot from a known good system
    - Mount drive A (Ideally as read only) (I'd probably use a USB connection for this)
    - Attempt file recovery (using a reputable file recovery solution) and see what I can get back
    - Repeat again with drive B.

    I fear you have learned that having data stored on a RAID 1 configuration does not always give you any benefits compared to even a single drive setup drive.

    I would suspect had you written the data to a single drive you wouldn't be in this pickle. Had you written the data to two separate drives you'd definitely have a backup (or at least two copies of bad data).

    To keep data safe, store it in multiple locations (RAID is not a backup) and verify each location can see and read the data.
     

Share This Page