Hot-swap CompactFlash card in USB reader?

Discussion in 'DIY Computers' started by Angus Rodgers, Feb 26, 2004.

  1. Like everyone else in the universe, it seems, I've just
    bought a Canon Powershot A60 digital camera (for £99.99
    from Amazon UK).

    To use with it, I bought a 128MB CompactFlash card from
    Crucial, along with their USB CompactFlash card reader.

    The instructions that come with it, on paper and on CD,
    are very sparse. The Crucial website isn't a lot more
    helpful, having only this to say on the topic of hot-
    swapping cards:

    "Do I have to turn the power off to remove my flash card?

    In most cases, no. As long as your device isn't currently
    accessing the card, you can usually "hot swap" one card
    for another without turning off the power, much the same
    way you would with a floppy disk on your computer. To be
    on the safe side, double-check the owner's manual for your
    device for specific instructions for removing and installing
    your flash cards. If you experience problems hot swapping
    the card, try turning off power before inserting the card
    to see if the problem is corrected."

    Not exactly definitive, when there is no "owner's manual"!

    I phoned their customer support centre, and was told that
    it is OK to insert or remove the card so long as the green
    light isn't on, i.e. data is not being transferred to or
    from the card.

    Although this is reassuring, I'd still like to know if it
    is safer or more reliable to detach the card reader from
    the USB port before either inserting or removing a card.
    I'll be inclined to play safe unless told authoritatively
    that it makes no difference.

    The reader comes with a cable having at one end a USB
    plug to connect to the computer, and at the other end
    a USB socket to connect to the reader (which I suppose
    could in principle be plugged straight into the PC).

    Common sense suggests that although it is harmless to
    leave the cable always plugged into a free USB port on
    the PC, hot-swapping the card at a time when the reader
    is already plugged into the PC is more likely to cause
    problems than hot-swapping the reader and card together
    as a unit - i.e. always inserting or removing the card
    when the reader is not connected to a power source.

    But is (my version of) common sense right about this?
    Angus Rodgers, Feb 26, 2004
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  2. Angus Rodgers

    Phöènix Guest

    Methinks you worry too much.

    As long as you are not actively writing to, or reading from, the card you
    have no worries. That is the only common sense you need to apply.

    I wouldn't know about your questionable logic above but I would say it
    should be irrelevent and unnecessary.

    I have been using CF and readers for a long while and never had to concern
    myself with such dilema.
    Phöènix, Feb 26, 2004
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  3. That sounds fine in theory, but in practice it turns out to
    be a second source of worry!

    Today I tried out the reader, and the green light stayed on
    even when I was not (knowingly) reading from or writing to
    the card.

    I phoned the customer service people again, and this time
    (following two hurried consultations with a supervisor) was
    given information that flatly contradicted what I was told
    yesterday. I won't go into all the boring details, but it
    sounded as if they were just guessing (at how the reader
    behaved with Windows 98SE).

    They had no answer to my worry that Windows 98SE might be
    accessing the device in some way even after I had finished
    copying the image file to disk.

    They ended up advising me (without prompting!) to play safe,
    in just the way I already planned to, i.e. by disconnecting
    the reader from the PC before removing the card. The story
    now is that the green light only indicates that the power
    is on - but they just didn't seem sure!

    In view of their apparent confusion (and in spite of your
    sanguine response), I thought I'd better double-check, and
    it may have been a good thing I did. There was a new icon
    in the System Tray, which, when I right-clicked or double-
    clicked on it (I forget which), gave me the option of
    "stopping" the removable drive (which was how the reader
    was represented in Windows). At first, when I tried to do
    this, nothing seemed to happen, and then when I tried again,
    I got a message warning me:

    "It is not safe to remove the device at this time"
    (or words to that effect)!

    Then I got a message saying the device had been removed;
    and indeed I was able to disconnect the reader, remove
    the card, and replace it in the camera, with no apparent
    harm done.

    But an instruction manual would have been a great help
    (if only to explain what the effing green LED is for).

    Oh, and I was also worried because there seemed to be no
    clear indication which way up the card should be inserted,
    but I seem to have guessed this right. Customer Service
    said that the card could be inserted upside down, but that
    this would do no harm (although the card would of course
    be unreadable); but should I believe them?

    Still, at least Crucial have a fairly prompt (and free)
    customer service facility, and the product does seem to
    work, and it was good value for money, so probably all's
    well that ends well, and with 20/20 hindsight I needn't
    have worried. Probably.
    There is indeed no substitute for experience, and I guess
    I'm learning the hard way.

    (Now to get round to replacing my second crashed hard disk,
    and diagnosing the AGP/graphics card fault that I never got
    round to fixing before the *&%%$$£&! disk crashed - perhaps
    because I was too busy soldering together the network cable
    that the hamster chewed through, reinstalling Windows after
    the first hard disk crash, replacing the broken VCR and CD
    player, and getting a new fridge installed, all of this
    happening at the same time as Christmas and my daughter's
    birthday, after I'd spent a fortune on an electric guitar
    that she's not using.) :(
    Angus Rodgers, Feb 27, 2004
  4. Angus Rodgers

    Phöènix Guest

    This is where you lost me yesterday. What makes you think disconnecting the
    reader while the card is being written to is any safer than removing the
    Phöènix, Feb 27, 2004
  5. No very good reason, just: (i) I'm fairly familiar with USB,
    but not at all familiar with CompactFlash; (ii) USB has small
    number of big chunky connectors, while CompactFlash has large
    number of teensy delicate little connectors, hidden inside,
    making me nervous; (iii) anything connecting to a USB slot
    is known to be likely to be easily hot-swappable, whereas I
    just don't know how robust CompactFlash is in this respect.

    OK, so (i), (ii) and (iii) aren't very distinct, but I said
    they weren't very good reasons! I don't think one needs to
    have very good reasons, though, to be nervous of unfamiliar
    technology (especially if there is no instruction manual).

    Call it instinct.
    Angus Rodgers, Feb 27, 2004
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