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Question hdd badblock interference and dvd burn

Discussion in 'General Electronics Discussion' started by johnmullins, Aug 27, 2020.

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  1. johnmullins

    johnmullins

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    Aug 27, 2020
    If I have an HDD with some badblock and reallocated sectors count, when I download files from the internet or copy files from a media to the HDD will these files be saved in these defective sectors of the HDD and will they corrupt? after that i burn a DVD disc will that burn also be corrupted?
     
  2. bertus

    bertus Moderator

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    Nov 8, 2019
  3. johnmullins

    johnmullins

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    Aug 27, 2020
    Who blocks the bad sectors, Windows or HDD? this block of the defective sectors of the HDD does not receive files is automatic or I will do this block manually?
     
  4. Audioguru

    Audioguru

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    Sep 24, 2016
    I am glad that my replacement computer has a Solid State Drive that is extremely fast. It is in an HP that is very new and I got it as a refurb last Black Friday for low cost.
     
    davenn likes this.
  5. kpatz

    kpatz

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    Feb 24, 2014
    Modern drives will reallocate bad sectors (blocks, clusters, etc.) from a pool of spares (when it detects them) and they will appear "good" to the operating system or end user, until it runs out of spare sectors to reallocate. Unless you look at the SMART data, you won't know from Windows (or other OS) that the drive has bad sectors, since to the operating system, the reallocation is transparent.

    Older drives (back in the 80s/early 90s) didn't do this, and instead bad sectors were visible to the operating system, and you could see how many you had by running Chkdsk (or Scandisk, or some other similar tool depending on OS). OSes still support this for legacy/compatibility purposes but it's rare to see bad sectors in Windows on a modern drive unless it's dying and the internal reallocation can't keep up.
     
    bertus likes this.
  6. bertus

    bertus Moderator

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  7. johnmullins

    johnmullins

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    Aug 27, 2020
    Who allocates the bad sectors of the HDD and prevents them from being used to write files? HDD or Windows? is this automatic or do i have to manually isolate these bad sectors? I've used PCs with HDD from the 2000s and Windows XP
     
  8. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    Did you read post #5 ?

    Bertus
     
  9. johnmullins

    johnmullins

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    Aug 27, 2020
    I just want to understand the name of this technology present in the HDD that allocates defective sectors preventing them from being used

    I know chkdsk but it is manual and many people don't know this command
     
  10. Martaine2005

    Martaine2005

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    May 12, 2015
    Low level programming language namely DOS detects unreadable or unwriteable sectors on older PCs. Those sectors are then blocked by the OS from reading or writing.
    I can’t be sure, but I think XP was the last OS to have DOS available to the user.

    Martin
     
  11. kpatz

    kpatz

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    Feb 24, 2014
    Back in the old days, when you bought a hard drive (usually MFM or RLL type), it would usually have a sticker on it with the locations of bad sectors printed on it, as the drive was tested in the factory. When you low level formatted the drive, you'd enter these locations into the formatting tool, and it would mark the sectors on the disk as "bad" so they would return an error when read. This is done because, sometimes a bad sector could be read successfully depending on what was written to it, so it would be unreliable, and not always caught in a simple read test done during formatting.

    Then when the high-level format was done (the Format command in DOS or formatting in Windows), which lays down the file system, would read scan the disk, identify the unreadable sectors (due to errors or due to being flagged as "bad" during LLF) and mark them in the file system as bad so the operating system wouldn't attempt to use them. These would show up as "bad sectors" on a CHKDSK report, and they wouldn't be used.

    If a sector failed later on, you'd get I/O errors, and you'd have to use a tool (like Norton Utilities) to attempt to recover the data and mark the new bad sector as bad. If multiple sectors started going bad over a short time, it meant the drive was failing and had to be replaced.

    When IDE hard drives started appearing (which evolved into today's SATA and other newer types) the controller was moved onto the drive itself so the low level format and remapping of bad sectors was handled at the factory, and the drive only needs to be partitioned and formatted for your operating system. Additionally, the SMART system started being used which allowed the drive to diagnose itself and detect certain types of failures including bad sectors on the fly. With these drives (which include modern SSDs), some "spare" space is reserved for reallocation of bad sectors that are detected, and bad sectors are not normally exposed to the operating system, so you generally won't see "bad sectors" when looking at the properties of a file system on a modern drive. If a bad sector is detected during operation, the drive firmware itself handles the remapping. The only time the OS is aware of an error is if a sector that has existing data on it goes bad and can't be read.

    Sometimes a drive will show an error in the SMART report but the sector isn't reallocated. This is probably a sector that had a soft (recoverable) error. For example, power was cut while the sector was written to so it got corrupted. It was unreadable, but after being overwritten later on, it was good again. Reallocation only occurs if repeated writes and re-reads fail, indicating a physical bad sector. If your drive only has a small number of reallocations and they don't increase, the drive is still good. But if you start seeing the error counts increasing on a regular basis on a drive, especially if the reallocated sector count starts climbing, it's time to get that drive out of there since it's going bad.

    And it goes without saying, but backups are always important! Not all drive failures can be predicted with SMART. A drive can fail suddenly and completely. A power surge can fry the board for example. Or you get the "click of death" next time you power it on.

    As for the OP's question, keep an eye on the SMART data for the drive. If the error totals are small and stay constant and don't go up when doing a lot of reads and writes to the drive, it's probably ok. If they are going up, that drive can't be trusted.
     
  12. bertus

    bertus Moderator

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    Nov 8, 2019
    Hello,

    Once I had a drive with SMART capability.
    It was about to fail and at startup of the system I got the message:
    immediately make backups and replace the harddisk.

    Bertus
     
  13. johnmullins

    johnmullins

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    Aug 27, 2020
    Which function is performed to allocate and isolate defective sectors of the HDD automatically without having to run chkdsk?
     
  14. davenn

    davenn Moderator

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    1,970
    Sep 5, 2009
    OK this thread is going in circles

    @johnmullins you seem to refuse to listen to what these good people are telling you
    You dont seem to be reading their links, else you wouldn't be asking the same Q's over and over

    Thankyou to everyone who tried to help :)


    thread closed
     
    Last edited: Aug 29, 2020
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