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Undelete Files With Bad Sectors

Using Dart Undelete XP with drives that have bad sectors. Hard drive manufacturers have the monumental task of designing a device to store data knowing that by design, the device will fail. The shear physics of a hard drive make it doomed to failure. The steps that manufacturers have done to lessen data loss are two fold.

First, there is the implementation of the S.M.A.R.T. technologies. This system was designed to give the user a heads up when the drive may be failing. Several components such as drive speed, track to track time, head placement and many other tests are performed on the drives daily. These tests are used in a comparison over time manner and can show a pattern of device degradation. During the degradation cycle there is a manufacturer assigned percentage used that will alert the user of impending data loss. For instance, if a drive has been spinning at 7200 RPM for several months, then over the last several weeks the RPMs drop to 7000 RPM, this may be flagged as an impending problem and the user will be notified that possible data loss may occur in the near future. It is up to the user to backup the data and replace the degrading device.

Secondly, built in to every hard drive is a sector map. This map consists of two lists. The primary list, which is set at factory, maps all bad sectors out. These bad sectors are found and mapped before the drive is sold. In other words, hard drives are expected to have bad sectors. There is no such thing as a perfect hard drive. The reason for this is that a hard drive would cost several thousand dollars if procedures were introduced that would guarantee a perfect hard drive. In order to keep costs down drive remapping is used.

Now, once the list of all the bad sectors are made at the factory the drive is then shipped and sold. As the drive performs its day to day functions more bad sectors will appear. It is inevitable. These bad sectors are then mapped to another list. Both of the bad sector lists are mapped to a reserved area of the hard drive. There are only so many reserved area sectors for the firmware to remap to. Once these sectors are exhausted the firmware cannot remap and the bad sectors become part of your live data.

Signs that a drive has used its reserved sector area are, slow reads, slow boot sequence, operating system may seem to lock, may have to reboot several times before the operating system comes up. A chronic bad sector problem will eventually cause file loss, and ultimately the drive will not be able to identify itself to the BIOS and your data is either lost, or can be very expensive to recover.

If your drive is in a state where you have several bad sectors and you then either delete files, or the files just “disappear” the following is a list of symptoms that DART Undelete may exhibit.

  1. It may take several minutes before the logical drive list is created. This is because you may have a slow reading, or intermittent reading sector(s) in the operating system boot area, or parameter blocks. The Master File Table primary entries may also have the same type of sectors.
  2. The scan and build of the file list may take a very long time if bad sectors are embedded in the Master File Table. The Master File Table is the table of contents for your entire drive and tells the operating system where all your data is stored. If bad sectors are found in the Master File Table, then your problems have been compounded to an even higher degree and file loss is almost guaranteed.Three, during the copy of the deleted files to another drive the copy runs sluggishly. The copy could actually look as if it is frozen and the operating system may appear to be locked up. This is an indication that there are bad sectors in the data itself and the file you are trying to recover will more than likely be corrupt.If DART Undelete exhibits one or more of these symptoms all is not lost. However, using DART Undelete to try and recover the files using the standard method when you have bad sectors may actually exacerbate the problem on the drive and could eventually cause more data loss. So, the first thing to do is to stop using the software on a damaged drive. The next this to try is outlined in the following steps.

    Using Dart Undelete Data Recovery Software

    In order to recover deleted files from a drive that has bad sectors embedded in either the Operating System Boot Area, Master File Table, or Data Area it is necessary to move the data from the damaged drive to another working hard drive. To do this, you must use a piece of drive cloning software. There are several pieces of software that will clone drives for Windows, however, using cloning software in Windows can cause more problems.

    Here’s why.

    When software makes a request for a sector read from the hard drive it is passed to the operating system, the operating system then sends the request to the device driver, the device driver then sends a request the kernel. The kernel runs at ring zero. The kernel passes the request to the bus, the bus to DMA, then the firmware on the drive, and finally the head is engaged, moved to the proper cylinder, and the correct sector is read. The data is read, sent to DMA, this is then passed to kernel memory, then passed up to operating system memory and finally the application receives the sector data. Each one of these steps has a CRC check, some have multiple CRC checks, as well as compression checks and a plethora of other data checks. If any of these checks fail, the step will retry. You can have as many as a thousand retries for a single sector read request. If the request is at ring zero, that is considered a priority request and the operating system will sit and wait for a response. This is when the application seems to lock up, or freeze. It can actually slow the operating system down due to the prioritized task manager.

    With all of these requests for a single read, an already damaged drive is grinding away trying to pull the data off of the platter. The retries will actually wear down heads, platter media, it will heat up the drive so that the spindle will heat and the viscosity of the lubricant on the spindle can degrade and will eventually freeze the drive like an automotive engine with no oil. What we want to do here is to minimize the amount of read retries. The best way to do that is to run a simple operating system, and an application that does not have any retry requests. DTIDATA has such a piece of software, it is called Speed Clone and it runs from a floppy and uses FreeDOS as its operating system. The software is $49.50 and can be found on our website for download. There is also Knoppix for Linux that will allow you to use Linux cloning tools to copy the data from one drive to another. Knoppix can be a bit overwhelming for anyone who is not familiar with Linux, but, it is an excellent tool.

    Once you have decided on the proper imaging software you are going to have to place your source, and destination drives in the computer to do the copy.

  • Open your computer and take out the bad drive.
  • Make that your master drive by setting the jumpers on the drive.
  • Take the drive that you are going to make the image on and make that your slave drive.
  • Place the drives back in the computer with the proper cabling and air flow set up.
  • Make sure that you have at the very least a 450 watt power supply in order to run all the fans, and hard drives that are now in your computer.
  • Place Speed Clone in the floppy drive and boot your computer.
  • Make sure that your BIOS is set to boot from the floppy first, then any other media. You want Speed Clone to boot the system.

If you have set up the software properly the operating system will boot right into the software. Both your drives should now be displayed in the window of Speed Clone. Since you have made the hard drive with the bad sectors the ‘master’ that drive should show up first in your ‘Source Drive’ list.

Mark the first drive as your source drive, and the second drive as your destination drive. Before you begin the clone make sure that your source drive is the drive with the bad sectors, and the destination drive is the new drive. The destination drive must be the same size or larger than the source drive.

This is of primary importance, Speed Clone takes no prisoners. If you have set up the drives wrong, if you choose the wrong source and destination drives Speed Clone does not care, it will destroy all data on the destination drive by using the data from the source drive, so please be very careful when using the application.

Editors Note 11/20/06: For a step by step tutorial on how to set up a slave drive with pictures and everything visit our “Data Recovery Tutorial setting up a hard drive as a slave”

Speed Clone will make an image on the destination drive and any bad sectors will be copied as zeroes. In other words, no data will be copied. A list of bad sectors will be created by Speed Clone. This list can be printed out and you can make a determination of how corrupt the file system may be.

That is for another article, and exceeds the scope of this one. If the drive has more than ten thousand bad sectors in the first 3 gigabytes of the drive, that’s not good and your file system will probably be fairly corrupt. If you have more than fifty thousand bad sectors in the first twenty to thirty percent of the drive that is also bad and your data as well as the file system is probably corrupt.

No matter, once the clone is finished reset your system to boot from XP, and make the new cloned drive the slave. All you need do now is run DART Undelete as normal and copy your deleted files onto the master drive. Everything depends on how clean your clone is. The fewer bad sectors, the better the data recovery will be.

Download DART Undelete:
DART Undelete File Recovery Software

4 Responses to “Undelete Files With Bad Sectors”

  1. Ed November 14, 2008 10:53 pm #

    I have two questions, but I will post them in separate posts for simplicity.

    Can SpeedClone be run from a bootable CDRom? Floppy Drives are becoming as rare as hens’ teeth.

    For that matter, how about a bootable USB thumbdrive?

  2. Ed November 14, 2008 10:56 pm #

    Second question.

    Your articles all talk about slaving drives, am I correct in assuming this is only in the IDE world, and SATA drives will be configured differently? I imagine the only trick with SATA will be ensuring you are absolutely sure of Source and Target, perhaps being careful by watching drive types or labels?

    Thank you in advance for both my questions.

  3. DTI Data Recovery November 15, 2008 11:06 am #


    Question 1: yes speed clone can be put on a bootable CD. We have an ISO file that we send after purchase. As far as thumb drives go, that is a good question. Since the floppy version is an .exe and the cd version is an iso, if your thumbdrive can boot i.e san disk cruzer lock, than you should be able to run the .exe, but I will forward this to Jacqui Best who is the software tech person. You can also call her on Saturday at 727-345-9665 and hit the option for software tech support. She is the one who would be sending you the files anyway.

    Question 2:
    You can absolutely slave a SATA drive. And like you said, the critical part is in knowing which drive is which. If you are going off of a motherboard then there will be a disk 0 and a disk 1, you will need to check which is which on the board itself. If you are using a SATA card it is pretty much the same, you will need to figure out which port is which drive. Within SpeedClone it will show the drive header, so if they are from different manufacturers you would know that.

    It is absolutely critical to know this info since if you hook it up backwards it will clone the new drive overwriting the old drive with 0’s


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