How does PC know what kind of file system the mass storage device has? - Storage

This is a discussion on How does PC know what kind of file system the mass storage device has? - Storage ; After reading the "USB Mass Storage Class Bulk-Only Transport" specification, I got a concept about the transmission protocol between my desktop PC and some portable USB devices such as external HDD and external DVD-RW. Despite this, I have no idea ...

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Thread: How does PC know what kind of file system the mass storage device has?

  1. How does PC know what kind of file system the mass storage device has?

    After reading the "USB Mass Storage Class Bulk-Only Transport"
    specification, I got a concept about the transmission protocol between
    my desktop PC and some portable USB devices such as external HDD and
    external DVD-RW. Despite this, I have no idea about how my desktop can
    understand the content in the storage media of the mass storage
    device. We know the file system is different between HDD and DVD-RW.
    Moreover, the file system of a optical disc maybe one of ISO9660, UDF
    or UDF bridge...etc. I think after the USB cable is attached, the
    device firmware can tell desktop its manufactory information to let
    desktop know it is a HDD, CD-RW or DVD-RW. But, how does PC know what
    kind of file system the device has?

    Could anybody give me any hint or reference document?

  2. Re: How does PC know what kind of file system the mass storage device has?

    > desktop know it is a HDD, CD-RW or DVD-RW. But, how does PC know what
    > kind of file system the device has?


    It reads the important sector locations from the disk and tries to recognize
    the filesystem.

    --
    Maxim Shatskih, Windows DDK MVP
    StorageCraft Corporation
    maxim@storagecraft.com
    http://www.storagecraft.com



  3. Re: How does PC know what kind of file system the mass storage devicehas?

    Smile ^_^ wrote:
    > After reading the "USB Mass Storage Class Bulk-Only Transport"
    > specification, I got a concept about the transmission protocol between
    > my desktop PC and some portable USB devices such as external HDD and
    > external DVD-RW. Despite this, I have no idea about how my desktop can
    > understand the content in the storage media of the mass storage
    > device. We know the file system is different between HDD and DVD-RW.
    > Moreover, the file system of a optical disc maybe one of ISO9660, UDF
    > or UDF bridge...etc. I think after the USB cable is attached, the
    > device firmware can tell desktop its manufactory information to let
    > desktop know it is a HDD, CD-RW or DVD-RW. But, how does PC know what
    > kind of file system the device has?


    The USB bulk-only transport is used to carry SCSI commands
    and responses. The SCSI INQUIRY command returns information
    about the type of device, as well as manufacturer and product
    information.

    > Could anybody give me any hint or reference document?


    dpANS Project T10/1236-D SCSI Primary Commands - 2

    Once you crank it up, its just reading blocks
    (typically 512 bytes each).

    The MBR (Master Boot Record) describes the partitioning
    and individual partitions contain various file-systems,


    --
    Michael N. Moran (h) 770 516 7918
    5009 Old Field Ct. (c) 678 521 5460
    Kennesaw, GA, USA 30144 http://mnmoran.org

    "So often times it happens, that we live our lives in chains
    and we never even know we have the key."
    The Eagles, "Already Gone"

    The Beatles were wrong: 1 & 1 & 1 is 1


  4. Re: How does PC know what kind of file system the mass storage device has?

    "Maxim S. Shatskih" wrote in message news:...
    > > desktop know it is a HDD, CD-RW or DVD-RW. But, how does PC know what
    > > kind of file system the device has?

    >
    > It reads the important sector locations from the disk and tries to recognize
    > the filesystem.


    But, as my understanding, the "important sector" is different between
    HDD and optical disc. For HDD, we can get file system parameters from
    sector 0 but for disc, we might need sector 16 to recognize its file
    system. Because PC only can use UFI commands(like SCSI commands) to
    communicate with device, does PC know which sector it should request
    after it knows what kind of peripheral the device is? I guess there
    should be a scheme which defines what data PC should request at first.
    However, I don't know how to find related articles efficiently by
    Google yet.

  5. Re: How does PC know what kind of file system the mass storage device has?

    > communicate with device, does PC know which sector it should request
    > after it knows what kind of peripheral the device is? I guess there


    The OS kernel - be it Windows or UNIX - enumerates all filesystems and asks
    each one to mount. If the FS returned OK - then all is done. If the FS returned
    error - then the next FS is tried.

    UNIX also supports only trying a particular filesystem, Windows does not.

    So, FSs execute the recognition sequence themselves, and are free to issue any
    reads they want. CDFS will read sector 16. UDF will read sectors 256, N and N -
    256. FAT will read sector 0, and so on.

    All of this is the issue of the OS kernel, not of the hardware. Hardware can
    only execute CDBs.

    --
    Maxim Shatskih, Windows DDK MVP
    StorageCraft Corporation
    maxim@storagecraft.com
    http://www.storagecraft.com



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