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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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Volatile USB RAM disk?

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    Volatile USB RAM disk?

    I've got a bit of an unusual problem.

    I need a USB (or other) RAMdrive that will persist across boots (e.g. rebooting operating systems) but not across power cycles.

    In other words, I need assurance that once power is off, the data is gone. (I've got some paranoid customers)

    Does anyone know of such a beast? Ideally, it would be something like a USB flash drive but with volatile RAM instead of flash.

    I know that a few years ago, Super Talent marketed a RAM cache USB drive, but the only used specimens available are being scalped for stupid dollars (50-100x original cost)
    Last edited by Chuck(G); February 12, 2017, 11:46 AM.
    Reach me: vcfblackhole _at_ protonmail dot com.

    #2
    Does it have to be external?

    How about an internal PCI card Gigabyte GC-RAMDISK i-RAM (with the backup battery removed)?
    http://www.ebay.com/itm/272550201986

    Comment


      #3
      Maybe, will it survive across booting? But SATA is out of the question (can't go into why)

      I need perhaps 150MB tops. I wonder if I could take a cheap RPi or some such and configure it to work as a USB device rather than a host.
      Reach me: vcfblackhole _at_ protonmail dot com.

      Comment


        #4
        Originally posted by Chuck(G) View Post
        I've got a bit of an unusual problem.

        I need a USB (or other) RAMdrive that will persist across boots (e.g. rebooting operating systems) but not across power cycles.
        IOW, a RAMdrive that will still contain the data after a warm boot, e.g., a 'Restart' from the Shut Down menu but not after a cold boot.
        PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

        Comment


          #5
          So, it will contain data if I start with Win98SE and switch to Linux on reboot? Clearly, if there are special device drivers involved, this is a non-starter.
          Reach me: vcfblackhole _at_ protonmail dot com.

          Comment


            #6
            Hey, slow down... I haven't even found a RAMdrive that survives a warm boot let alone one that doesn't use a device driver, either.

            It seems that you need a piece of semi-volatile hardware, whatever that is.

            Otherwise, a script would work for you.
            PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

            Comment


              #7
              Build a cheapo widget out of a PIC which will generate a random number on powerup and report it via (or something). Then use that as the key for an encrypted drive. When the power goes out, the key gets lost, and the data on the drive is inaccessible.

              It's possible that something like a Yubikey will already have this functionality.

              Comment


                #8
                You can easily do it with any SoC board that supports peripheral mode USB. Pi, Pi Zero, PCM, Intel compute stick, chromecast, etc, etc. You just need to power it externally from the host system you have it plugged into in-case the host system drops power periodically during the boot process (as drivers initialize/reinitialize). Linux has a gadget driver for USB mass storage class. You just point it to a file to use as a block device. That file can be one created on a tmpfs file system (RAM disk). Would be pretty trivial to do it on any Pi.
                "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

                Comment


                  #9
                  How would it work on the Win98SE side? Use the mass storage update to see the usb device?
                  Last edited by Caluser2000; February 12, 2017, 02:14 PM.
                  Thomas Byers (DRI)- "You'll have a million people using the A> [MS-DOS prompt] forever. You'll have five million using [nongraphic] menu systems such as Topview, Concurrent PC-DOS, Desq, and those types. But there'll be 50 to 100 million using the iconic-based interfaces."

                  Comment


                    #10
                    Originally posted by Chuck(G) View Post
                    Maybe, will it survive across booting? But SATA is out of the question (can't go into why)

                    I need perhaps 150MB tops. I wonder if I could take a cheap RPi or some such and configure it to work as a USB device rather than a host.
                    add on a usb/sata converter? it's a bit of a kludge, but should work.
                    It is a mistake to think you can solve any major problems just with potatoes.

                    Comment


                      #11
                      Originally posted by eeguru View Post
                      You can easily do it with any SoC board that supports peripheral mode USB. Pi, Pi Zero, PCM, Intel compute stick, chromecast, etc, etc. You just need to power it externally from the host system you have it plugged into in-case the host system drops power periodically during the boot process (as drivers initialize/reinitialize). Linux has a gadget driver for USB mass storage class. You just point it to a file to use as a block device. That file can be one created on a tmpfs file system (RAM disk). Would be pretty trivial to do it on any Pi.
                      That's my thought. An Orange Pi (maybe even a Pi Zero) should do the trick, but I have to find out if it's trivial to get the USB port to act as a device. A OP has between 512MB and 1GB of DRAM, which should be more than enough for my purposes.
                      Reach me: vcfblackhole _at_ protonmail dot com.

                      Comment


                        #12
                        The Amiga using DOS 2.0 or higher used the RAD: device.
                        Rick Ethridge

                        Comment


                          #13
                          You do have to use a Pi that doesn't have a USB HUB in the way. eg. a Zero.
                          "Good engineers keep thick authoritative books on their shelf. Not for their own reference, but to throw at people who ask stupid questions; hoping a small fragment of knowledge will osmotically transfer with each cranial impact." - Me

                          Comment


                            #14
                            You also have to hope you never run into the Raspberry Pi's USB data corruption problem which has never been totally solved.

                            Comment


                              #15
                              The Pi Zero emulating a flash drive is a good thought...and set it up to store the data file in ramdrive space (/run/shm). Only question is if powering it on and off improperly, such as would likely be the case with something like this, would corrupt the on-board SD card. I guess there is also the question of whether the customer would trust something like that which has an SD card on board, even though it's not writing the data to it...

                              I know Arduinos can be configured to pretend to be USB HID devices...I wonder if there's any way to make one of them be a flash drive? Trick would be somehow connecting DRAM or the like to it. Probably a long shot...just thinking out loud.

                              Wesley

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