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

    From nospam@needed.invalid@1:124/5013 to All on Thu Jan 31 19:16:25 2019
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    From: Paul <nospam@needed.invalid>
    Newsgroups: microsoft.public.windowsxp.general
    Subject: Re: What is the difference between a regular Format and a Low Level
    Format?
    Date: Wed, 22 Nov 2017 20:24:10 -0500
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    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
    --- Platinum Xpress/Win/WINServer v3.1
    * Origin: Prison Board BBS Mesquite Tx //telnet.RDFIG.NET www. (1:124/5013)
  • From nospam@needed.invalid@1:124/5013 to All on Thu Jan 31 19:16:25 2019
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    From: Paul <nospam@needed.invalid>
    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 05:25:41 -0500
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    Ian Jackson wrote:


    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?

    That sounds like a 48 bit LBA problem (cuts in at >137GB, 120GB
    drives OK, 160GB IDE drives could deliver a surprise). That's a problem
    on IDE drives, before ATA/ATAPI 6 or so. Seagate offered a document
    on the topic, which is a place to start, but not the end of the
    story. Some of the pronouncements in here are overly pessimistic.

    http://web.archive.org/web/20070121085230/http://www.seagate.com/support/kb/dis c/tp/137gb.pdf

    Older IDE hardware, before 2003, supports 28-bit LBA, and that
    causes a limitation in practical partition size. If the address
    rolls over in hardware, an attempt to write to the 137GB mark,
    ends up writing to location zero, wiping out the file
    system header or other valuable goods.

    After 2003, more BIOS and hardwares were claimed to support
    48-bit LBA, which significantly extends the address space.
    There was an announcement by one of the motherboard companies,
    that all their stuff supported 48-bit on IDE, after a certain
    magic date. I think it was 2003, but my memory isn't very good.

    The original proposal to the standards body, on how to do this,
    is documented here (the year 2004 is the first time Archive.org
    took a snapshot). It was a "double-pumping" of some registers,
    to cause fewer interface changes or something. On page two, it
    shows how an extended set of information, is loaded, via the
    pattern in the upper table. That's how they fit 48-bits.

    https://web.archive.org/web/20041024150852if_/http://www.t10.org:80/t13/technic al/e00101r6.pdf

    I thought the behavior of Windows handled this pretty well.
    I'm surprised the boot was a problem. For example, Win2K SP2
    won't make a partition larger than 137GB on a 160GB disk,
    so it won't get into trouble. (That's because Win2K SP2 can
    also corrupt a larger hard drive, given a chance. Win2K SP2
    was doing the best job it knew how to do.) But if a second partition
    happens to span the 137GB mark, that could easily cause
    corruption. You can "import" a drive from a more modern OS,
    and have it ruined by Win2K SP2 (SP4 is OK).

    x 137GB
    <--------------------------><----------------------------------->
    Partition below 137GB Partition spanning 137GB = trouble
    is OK and works by itself |
    |
    ^ | A write to 137GB, goes down to zero,
    +-------------------------------+ corrupting the first partition or MBR

    *******

    Using another OS drive, boot the system and do your forensics
    on the 160GB drives that aren't behaving themselves. It could
    be that the OS partition is completely trashed. See if you
    can spot the "NTFS" string in the first sector of the
    partition for example. A copy of HXD could help, as it has
    an option to open a hard drive for low-level access. You will
    have to take your best shot at the math to work out where
    the partition(s) start and end. I like PTEDIT32 for this
    purpose - it's a great help, and it was easily available up
    until a year or two ago.

    https://mh-nexus.de/en/hxd/

    *******

    If you want to "cheat death" and you have the time to spend,
    try pre-formatting the 160GB drive. Say, make a 100GB partition
    and format it NTFS. Now, put it in the system where you'll be
    doing the install. Tell the installer to install in the
    100GB partition (not above that). When you boot, it should work.
    Don't allow the installer to pick its own size (it indeed, that's
    how this mess was caused). Maybe you were using a WinXP Gold year 2002
    or so CD ?

    Paul
    --- Platinum Xpress/Win/WINServer v3.1
    * Origin: Prison Board BBS Mesquite Tx //telnet.RDFIG.NET www. (1:124/5013)