Bad Block in Drive

Discussion in 'backup, imaging & disk mgmt' started by BrianQwerty, Mar 2, 2021.

  1. BrianQwerty

    BrianQwerty Registered Member

    Feb 27, 2021
    John Day Oregon
    any programs out there that are free or open source that will fix/reallocate bad blocks...

    or well fix a bad block?....move a bad block....ect

    bad block in drive... when you find them with a surface scan.
  2. Brian K

    Brian K Imaging Specialist

    Jan 28, 2005
    NSW, Australia
    I'd try (X: is the drive letter)

    CHKDSK X: /R
    How many bad sectors are reported when this has completed?
  3. manolito

    manolito Registered Member

    Apr 23, 2013
    AFAIK modern SATA drives should never report any bad blocks with CHKDSK. The internal controller of the drive should take care of bad blocks and reallocate them so they will not get used any more. To the outside world the drive lies about the real sector numbers so it will look flawless. You can see the numbers of reallocated sectors through any SMART diagnostic software.

    Having said this it does happen sometimes (for me mostly after a sudden power outage) that the automatic reallocation does not work. For these situations I mostly had succes applying a LOW LEVEL FORMAT to the drive. Please note that this name is misleading. It has nothing to do with the "real" low level format which was incorporated in the external drive controllers of ancient HDDs before the internal IDE interface was invented. This low level format could be invoked by users with the DOS Debug.exe utility, and it really did initialize the drive physically.

    Today all tools which perform a so-called Low Level Format just overwrite the whole drive with zeros. This gives the internal drive controller a chance to reallocate all the bad or weak sectors it detects. After performing this task and repartitioning / formatting the drive chkdsk should no longer report any bad sectors. If it still does then chances are that the drive is physically damaged.
  4. A_mouse

    A_mouse Registered Member

    Jul 29, 2019
    A field
    Yes. You have 2 options.
    You can try rewriting the blocks either via the filesysem or RAW device access.
    Or use a SMART tool so you can get the drive to run its own tests. (DOS tool also included on the Ultimate Boot CD ISO) (Windows tool with a driver so it can access the drive at low level while in use)
    You can use the commercial HDDRegenerator to fix 1 block for free as a trial (often that is enough to make the drive readable again)

    You can run the various SMART self-tests such as the conveyance and extended tests which may take a couple of hours.
    The drive will only ever do the 2 minute basic test automatically, and only if it is enabled to do so.
    Most drives come with SMART enabled, and some have periodic self-testing enabled, but you should check this (enable all 3 options if available, but many only have the 2). (multi-OS CLI tool with many GUI options. Included with many Linux distros).
    My favoured Windows GUI is HDD Guardian (abandoned but you can update the core CLI tool from the link above.)

    Finally choose a SMART monitor you like the look of to keep you informed of the drive condition.
    Though drives may self-fix some problems, OSs only tend to say something if the drive is failing badly.
    Better to see the issues happen before they turn into actual failures.
  5. reasonablePrivacy

    reasonablePrivacy Registered Member

    Oct 7, 2017
    Member state of European Union
    I assume we talk about drives old technology called HDD, not newer SSD.
    Drive's internal controller may not reallocate sector you want to read. This sector may be reallocated, as you noted later, on write event to that sector. That's why scanning drive with read operations may discover new bad blocks.
    Second thing is that HDD have quite small number of spare memory, so if there is too many bad sectors there is no space to reallocate them transparently. Drive may just report them to the OS.

    You may want to run conveyance or extended SMART tests HDD anyway then overwrite bad block, so you give a chance for internal drive controller to reallocate them. It won't do it without overwriting sector, because there is small chance that one of subsequent read operations may miraculously end successfully.
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