• Re: What is the difference between a regular Format and a Low Level Fo

    From G6JPG-255@255soft.uk@1:124/5013 to All on Thu Jan 31 19:16:25 2019
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    From: "J. P. Gilliver (John)" <G6JPG-255@255soft.uk>
    Newsgroups: microsoft.public.windowsxp.general
    Subject: Re: What is the difference between a regular Format and a Low Level Format?
    Date: Thu, 23 Nov 2017 00:17:51 +0000
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    In message <191c1dtfqsvlh4uvv13oo23tul3j6jobq4@4ax.com>,
    james@nospam.com writes:
    What is the difference between a regular Format and a Low Level Format?

    I have a program to do Low Level Formats.
    I had a flash drive that somehow got screwed up. A regular format did
    not fix it, but a low level format got it working again.

    For disc (partition)s: it used to be that a "quick" format just deletes
    the entries in the root directory, thus making the disc (partition) look
    as if it has nothing on it (including sub-folders), whereas a full one actually did some sort of test on every sector, so that dud ones could
    be marked as bad and avoided (by in effect making notes of the dud ones
    on the disc somewhere). For modern discs where the disc firmware itself
    has something that does that, it at least exercises the disc.

    I'm not sure if "quick/full" is the same as "regular/low-level".

    For a floppy, a full format also in effect wrote something on the disc
    that was of use during subsequent operations, rather like drawing lines
    on a sheet of paper before you use it; a "low level" format of a hard
    disc used to do something similar, but again, in modern HDs that's
    probably done before it leaves the manufacturer and isn't really doable
    by the user.

    For your flash drive, I'm _guessing_ that the quick format - if that's
    what you did - just did in effect a "del /s *.*", which wouldn't have
    fixed it if the part that stored the root directory was corrupted,
    whereas the low-level format would have re-initialised it.

    But someone - Paul probably - will be along in a moment to say more than
    just my guesses (-:.
    --
    J. P. Gilliver. UMRA: 1960/<1985 MB++G()AL-IS-Ch++(p)Ar@T+H+Sh0!:`)DNAf

    Reality television. It's eroding the ability of good scripted television to survive. - Patrick Duffy in Radio Times 2-8 February 2013
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  • From ianREMOVETHISjackson@g3ohx.co.uk@1:124/5013 to All on Thu Jan 31 19:16:25 2019
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    Newsgroups: microsoft.public.windowsxp.general
    Subject: Re: What is the difference between a regular Format and a Low Level Format?
    Date: Thu, 23 Nov 2017 09:27:05 +0000
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    In message <ov57vn$1fql$1@gioia.aioe.org>, Paul <nospam@needed.invalid>
    writes
    james@nospam.com wrote:
    What is the difference between a regular Format and a Low Level Format?
    I have a program to do Low Level Formats. I had a flash drive that >>somehow got screwed up. A regular format did
    not fix it, but a low level format got it working again.


    A partition "Quick Format" assigns a file system to a partition.
    It has nothing to do with the workings of the disk drive itself.
    A Quick Format writes a FAT or $MFT, writes a file system
    header, and that's it. It doesn't check anything.

    A partition "Format" without the quick, does a read verify of
    every cluster after the same steps as the previous paragraph.
    If bad clusters are found, they're added to the $BADCLUS list.
    The intention is, with a regular format, to "block" any
    bad sectors so they cannot be used. A bad sector is
    defined as a sector returning a CRC error, where the
    automatic sparing can no longer repair it and keep
    the sector in service.

    *******

    A "low level" format is a disk drive technology, It has
    nothing to do with partitions or even OSes. It's something
    that happens at the platter level.

    Modern drives have a servo pattern recorded at the factory.
    The drive is only allowed to write to data sector areas.
    So all that a modern drive can do, is "zero" out the data.
    It's not allowed to change any other aspects of data content.
    As a result, there is no "low level" format on a modern drive.
    Even if a command existed in the ATA/ATAPI command set for
    it, only the data sector portion could be written.

    On an "old" drive, both the sector head and sector data
    areas are candidates for writes. During a normal write
    operation, only the sector data is written. During
    a "low level" format, both the sector head and the
    sector data are refreshed. And back in those days,
    if you interrupted the "low level" format, the
    disk tended to be ruined. When really you should
    have been able to start the process over again. It suggests
    at the end of the low level format, some info must have
    been written to the "critical data" section of the
    platter at "track -1". That's also the area where the
    drive firmware is kept (when you flash a drive, track -1
    gets the information stored there).

    A "low level" format can be beneficial to a flaky "old"
    drive, but you must not interrupt the process - even
    if the software looks like it's frozen :-/ Been there,
    and done that.

    Paul

    In the past few years, I've collected a load old/ancient disks, and used
    some of them to 'keep my hand in' doing XP installs on an old clunker
    PC. [These never seem to go the same way twice, but that's another
    story.]

    X-GSmartControl (and other tests) shows that quite a lot of these disks
    have a few minor historical errors, so I decided that it might be a good
    idea to do a low-level format on some of them (using HDD LLF Low Level
    Format Tool). This didn't seem to do any harm to the disks, but on one
    type (IIRC, all 160GB Seagate), when I tried to install XP, when it got
    to removing the installation disk and rebooting, the reboot came up with
    a blue screen showing the message "Unmountable boot volume" (and a lot
    more). IIRC, three Seagate disks did the exactly the same, but a couple
    of others (Maxtor 40GB, I think) were OK.

    So is this just a coincidence, or can a low-level format leave at least certain types of hard drives looking apparently OK - but unusable for installing an operating system on?
    --
    Ian
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