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Detrmining the size of the sector spare area

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  • Detrmining the size of the sector spare area

    Hi,
    I am interested in determining the size of the sector spare area - the area used by the hard drive to reallocate defective sectors. This information is not available through the manufacturer nor any utilities that I could find. Is there any way to simulate defective sectors so that when the upper limit is reached and the spare area is filled, a disk failure will be generated at which time I'll know how many bad sectors it took to fill the spare area.

    Thanks,

    Ernie

  • #2
    I don't know of any tool that directly reports this.

    But here is something interesting. If you get our DiskCheckup tool it reports these figures,
    Cylinders
    Tracks per Cylinder
    Sectors per track
    Total sectors.

    What I have noticed is that the Total sectors figure is less than one would expect from the other numbers. For example,

    Cylinders: 182401
    Tracks/Cylinder: 255
    Sectors/Track: 63
    Bytes/Sector: 512
    Total disk sectors: 2930277168

    Where as I would have thought Total disk sectors should be, 2,930,272,065.

    So 5103 sectors appear to be unaccounted for !!

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    • #3
      You should be able to get the information from the SMART data. It wont tell you exactly how large the spare sector map is but it will tell you how much of it is used. Combined with the trigger information as to percentages for a SMART failure and you should be able to determine with a fair amount of accuracy just how big the spares are.

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      • #4
        Originally Posted by Ernie Kaminaris
        Hi,
        I am interested in determining the size of the sector spare area - the area used by the hard drive to reallocate defective sectors. This information is not available through the manufacturer nor any utilities that I could find. Is there any way to simulate essay dune defective sectors so that when the upper limit is reached and the spare area is filled, a disk failure will be generated at which time I'll know how many bad sectors it took to fill the spare area.


        Hi Ernie,

        How did you manage that? I posted a similar question on the SuperUser forum. As I had an issue with the old drive, it was out of warranty and I got the "Reallocated Sector Count" is failing error. Seems to me I used SMART data then. But I can't find the topic now with the recommendations and my detailed report.
        Last edited by davidglines; 08-29-2019, 08:27 AM. Reason: typos

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        • #5
          What kind of drive? Presume this is Unix/Linux, where smart tools are available from GitHub, etc??
          If SSD, the smart tool needs to be SSD knowledgeable, as it is a tad different and you'd want to keep some track of write/erase cycles, failed writes, and the gas gauge.
          Some hdds may not report available space fully, as the drive vendors may only make one drive, but offer it in two capacities where one is half the other, where during mfgr part of the drive is masked off in drive firmware, and the return to smart may or may not be able to get the real space. But in any case, when a drive starts showing SMART errors [with or without scrub], there are items to look for:
          1. The remaining useable space for reallocation which isn't that important until it gets really low.
          2. The number of errors. Once this gets high, that drive is likely to keep failing until it depletes all available spare space. SSD drives can drop a lot of space in a hurry just based on how they are made.
          3. Error trajectory. An HDD that suddenly increases the error rate, and that keeps increasing is not a drive that will live too much longer no matter how much spare space is available.
          4. Write Erase errors on an SSD climbing. The spare space will deplete at scarily large values for the big multi-terabyte SSDs, but as long as this is reasonably intermittent and does not drastically increase the trajectory, the drive has pretty good odds of lasting a lot longer as long as the available space and gas gauge is ok.

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