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ufsdump dd tape guru's I need your help - Sun Solaris

I need some ideas on how I can access some lost data. I have a tape backup using ufsdump of several disks. The tape originally had the following file systems usfdumped to the tape: / disk1 disk2 disk3 the next night.. The painful part is disk1 failed. The backup ran in cron and the only thing on my tape is a ufsdump of disk3. Disk3 appears to be the first thing on the tape? The bus must of had errors and aborted the /, disk1, disk2 dumps. I need to get to the data on the tape for disk1 from ...

  1. #1

    Default ufsdump dd tape guru's I need your help

    I need some ideas on how I can access some lost data.
    I have a tape backup using ufsdump of several disks.

    The tape originally had the following file systems
    usfdumped to the tape:

    /
    disk1
    disk2
    disk3

    the next night..
    The painful part is disk1 failed. The backup ran in cron
    and the only thing on my tape is a ufsdump of disk3. Disk3
    appears to be the first thing on the tape? The bus must of
    had errors and aborted the /, disk1, disk2 dumps.

    I need to get to the data on the tape for disk1 from the
    previous nights backup. The ufsdump of disk3 should only
    be about 30MB. A normal usfdump of "/" is serveral GBs.

    I'm hoping with dd or some other utility I can still get to
    the ufsdump for disk1. I don't believe its been overwritten.
    Ufsrestore and the "mt -f /dev/rmt/0n fsf 1" commands fail to
    get me to past the first dump.

    System is a Solaris8 x86

    Hope I've explained that ok?
    thanks,
    Joe Guest

  2. #2

    Default Re: ufsdump dd tape guru's I need your help

    In <google.com> com (Joe Dietz) writes: 

    it is more likely that you used the "rewind on close" tape
    devices for the dumps instead of the "no rewind on close"
    tape devices. the result would be that the tape would
    be rewound after every dump and every dump over-writing the
    ones that came before it.
     

    whether or not you can get the tape drive to read past
    the end-of-tape marker depends on the mechanism. software
    tools alone may not help. you will also need to know how
    large the disk2 dump is, if it is large then there may
    not be much of disk1 left on that tape.
    ultrasparc3@hotmail.com Guest

  3. #3

    Default Re: ufsdump dd tape guru's I need your help

    com wrote:
     
    >
    >
    > it is more likely that you used the "rewind on close" tape
    > devices for the dumps instead of the "no rewind on close"
    > tape devices.[/ref]

    This is certainly possible, but I have seen situations where
    a tape drive will rewind after some sort of error has occurred,
    even when you use the no-rewind device.

    It's been a while since I've seen it, but I believe the
    scenario goes something like this:

    1. write some data to the tape.
    2. error occurs.
    3. close tape device; device is left in error state.
    4. backup script doesn't check status of tape; opens
    tape device again despite error. driver or drive's
    firmware responds by rewinding tape, then proceeding
    as normal.

    As I recall the situation, the rewinding doesn't happen
    until the device is opened again, but it might be the
    other way around. (The device might rewind when you close,
    if there's an error.)

    Also, I can't remember the type of error that causes this,
    but I believe it's either a full tape or a "Media Error".
    (I've seen enough of both that they sort of bleed together
    in my mind...)

    Anyway, the point is that my experience indicates that
    sometimes it is possible to have an error cause your
    tape start over at the beginning.
     
    >
    > whether or not you can get the tape drive to read past
    > the end-of-tape marker depends on the mechanism. software
    > tools alone may not help. you will also need to know how
    > large the disk2 dump is, if it is large then there may
    > not be much of disk1 left on that tape.[/ref]

    Yes, this is going to be tricky stuff. The way that it
    works is possibly going to depend on the type of tape
    drive. If you "man mtio", you'll see stuff about different
    types of tape drive handling end-of-file markers differently.

    One possible thing to try would be a "mt eom" followed by
    an "mt fsf 1". Also, this little bit from "man mtio" looks
    interesting:

    MTIOCREADIGNOREEOFS
    enables/disable support for reading past two EOF marks
    which otherwise indicate End-Of-recording-Media (EOM)
    in the case of 1/2" reel tape drives

    Whether that would work on various types of tape drive
    is a whole other question. (Somehow I doubt the original
    poster is using nine-track tapes...)

    - Logan

    Logan Guest

  4. #4

    Default Re: ufsdump dd tape guru's I need your help

    Joe Dietz <com> wrote: 

    Most tape drives (8mm, DLT, ...) will refuse to return any data past the
    last write. This is a drive enforcement. I don't know any way to
    override it.

    There have been some reports of users overwriting the EOT past the last
    write, then powering down the drive to prevent it writing another one,
    then rewinding and trying to get past it. I've tried that method twice
    (once on 8mm, once on DLT) and it didn't work for me either time. I
    don't recommend it.

    If you *really* think the data is on there, and its worth something to
    retrieve it, send the tape to one of the recover houses. They can do
    some remarkable things with tapes for a lot of money. Call them first
    and get a quote.

    --
    Darren Dunham com
    Unix System Administrator Taos - The SysAdmin Company
    Got some Dr Pepper? San Francisco, CA bay area
    < This line left intentionally blank to confuse you. >
    Darren Guest

  5. #5

    Default Re: ufsdump dd tape guru's I need your help

    Thanks everyone. I'm not sure its worth the big $s to try and get the
    data from the tape. I was just exploring to see if there were some
    cool utilities I could try...I'm going to bet these revovery houses
    have custom drivers and software written. I wanted to check with the
    net to see if there were any options before getting a quote.


    Darren Dunham <taos.com> wrote in message news:<G1Fbb.5325$news.prodigy.com>... 
    >
    > Most tape drives (8mm, DLT, ...) will refuse to return any data past the
    > last write. This is a drive enforcement. I don't know any way to
    > override it.
    >
    > There have been some reports of users overwriting the EOT past the last
    > write, then powering down the drive to prevent it writing another one,
    > then rewinding and trying to get past it. I've tried that method twice
    > (once on 8mm, once on DLT) and it didn't work for me either time. I
    > don't recommend it.
    >
    > If you *really* think the data is on there, and its worth something to
    > retrieve it, send the tape to one of the recover houses. They can do
    > some remarkable things with tapes for a lot of money. Call them first
    > and get a quote.[/ref]
    Joe Guest

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