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Empty USB Storage showing 1.39GB used (longish post)

Discussion in 'Android Devices' started by garryknight, Apr 24, 2012.

  1. garryknight

    garryknight Well-Known Member
    Thread Starter

    Just got my Galaxy S2 GT-I9100 on Saturday and set it all up. I'm now trying to understand the way the storage works. I know that my phone has 16GB of internal storage and can take a micro-SD of up to 32GB in size.

    According to the Storage tab in Task Manager, it has 1.97GB of System storage, 11.5 GB of USB storage, and - in my case - 29.23 GB of SD card storage. I'm trying to understand how the phone's internal memory is used, and how this maps onto the file system, especially since the figures show:

    System storage: 786MB/1.97GB
    USB storage: 1.39GB/11.50GB
    SD card 10.70GB/29.23GB

    I assume that the 16GB of internal memory is split into two partitions: 1.97 GB of system storage and 11.5 GB of USB storage, with the missing 2.53 GB presumably as 'overhead', i.e. used by the system somehow and not available to me, presumably because of the way the partitions are set out. Is this correct?

    Looking at the layout of the file system with ES File Explorer, I see the contents of my root directory, including all the usual suspects like /etc/, /lib, /proc, and /sbin, plus Android's /app-cache and /data. One of the subdirectories is /sdcard. If I look in there I find various subdirectories such as Android, Attachments, backups, Notifications, and Sounds, as well as data directories used by my apps.

    Then I see two other subdirectories: external_sd and usbStorage. I realise that external_sd is my 32GB micro-SD card. And at the moment, my usbStorage directory contains nothing whatsoever.

    So, if system storage is on one partition, and /sdcard is on another (so that it can be mounted, formatted, etc), then what is the usbStorage subdirectory? What is it used for?

    When I unmount my 'SD card' in Settings/Storage, everything below /sdcard is unmounted. So am I to understand that everything above /sdcard is held in the 1.97GB of system storage? If so, then /sdcard must be where the 16GB (11.5 GB available to the user) of internal memory is mounted. And external_sd is mounted below this.

    1.97GB /
    11.50GB /sdcard
    29.23GB /sdcard/external_sd
    0 /sdcard/usbStorage

    So, my main questions are:
    1) am I right about the way the phone's internal memory is laid out?
    2) what is /sdcard/usbStorage, and what is it used for?
    3) since my /usbStorage directory is empty, why does Task Manager show:
    USB storage: 1.39GB/11.50GB

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  2. DaveSyd

    DaveSyd Android Enthusiast

    Garry there have been several posts incl ones by me around Sept Oct last year so suggest you search there also.

    In short yes the 16GB internal contains 1.97G Gb internal - think of this like your system swap file your PC. When you load programs it consumes it but it unloads ones you are not using. You don't have to worry about it it's just there and managed by the system.

    11.5GB is your internal SDcard - was created before the OS really caught up with how to name and it may be called different things on different phones. Think of this like a hard disk drive D: on your PC

    The partition you cannot see is the Andriod OS itself and resevered as 2.53GB. If they didn't resever some extra you would not be able to upgrade the OS. Think of this as your system drive C: on your PC. You can access as read only with some tools eg. ES File Explorer is a good one, it starts by default in your /sdcard/ internal memory but if hit some settings and hit the up key you can see all the OS files. Fortunately you can't change them.

    /sdcard/usbStorage is where android mounts the external USB device you connect through the bottom MicroUSB. ie. like your PC, the phone can mount a eg. USB thumbdrive, or card reader. On eBay you will see hundreds of connecting cables MicroUSB to female USB - so called OTG On the GO. This function is limited since the phone does not have much power but certainly it will read thumbdrives, card read etc. plugged into the bottom. Search for "OTG USB". When you plug in a thumb drive it appears under /sdcard/USBStorage/A, B, C or D, usually A but then the file structure underneath. This folder has nothing to do with any storage reporting.

    Task manager is showing the empty space in "Internal storage" ie your internal swap drive (above) loaded with apps and the empty space in "USB storage" which is /sdcard/ internal. It will also show "SD card" which is microSd intalled if you have one.See how the names very depending on where you look but they are getting more consistent.

    garryknight and jayroller like this.
  3. garryknight

    garryknight Well-Known Member
    Thread Starter

    Thanks for such a clear and detailed reply, DaveSyd. I understood everything. I should have realised that usbStorage is the mount point for USB OTG. I ordered a cable a couple of days ago for use with a card reader and my camera's SD card so I can edit and upload pictures "in the field".

    I'll also be able to back up my phone directly to my powered USB hard drive without having /sdcard unmounted.

    Thanks again :)
  4. DaveSyd

    DaveSyd Android Enthusiast

    The "Thanks" button is right at the bottom there on the right ! ;)

    garryknight likes this.
  5. Slug

    Slug Check six!
    VIP Member

    More or less. :)

    There is 16GB of total internal storage. 2GB of this is defined as "system storage" and is the default installation location for apps. Otherwise this area is inaccessible to the user.

    Of the remaining 14GB, 11.5GB is available as "internal storage" and is mounted as /sdcard to allow the handset to be used without a microSD card. Devices without internal storage mount external cards as /sdcard so apps expect to see this mount point.

    The remaining 2.5GB can be thought of as reserved for the OS filesystems; a PC's boot disk, if you like.

    It's a mistake to think of it as a "subdirectory" in the DOS sense. It's simply a mount point that is only used when the device is connected via USB as a removable drive. In effect /usbstorage is /sdcard, but only one is mounted at any time depending on the circumstance. Similarly, /external_sd isn't really a sub-directory of /sdcard.

    See above. I think the label "USB Storage" in Task Manager is simply chosen to be descriptive and differentiate from "External SD card".
  6. garryknight

    garryknight Well-Known Member
    Thread Starter

    Clicked :)
  7. garryknight

    garryknight Well-Known Member
    Thread Starter

    OK, I assumed it was system ROM.

    I've been using Linux since 1998, but I realise that most people don't so I used "Windows speak". Sorry for talking down to everyone. ;)

    I've now got a clear idea of how the SGS2 manages memory and device-mapping. But where they refer (in Settings, Storage) to the 11.5GB built-in memory as "USB Storage" when in reality the only USB storage is whatever is plugged into the socket using a USB OTG cable, this is not only confusing, it's potentially dangerous. Anyone who clicks "Format USB Storage", thinking they're formatting an external SD card plugged in via their USB OTG cable, is in for a big surprise when they find they've just wiped their internal storage back to 11.5GB.
  8. Slug

    Slug Check six!
    VIP Member

    I only sought to make things clearer based on the available information, but apologies if you thought otherwise.
  9. garryknight

    garryknight Well-Known Member
    Thread Starter

    No need. That's exactly what I thought you were doing. The fault was mine :)
    Slug likes this.

Samsung Galaxy S2 Forum

The Samsung Galaxy S2 release date was April 2011. Features and Specs include a 4.3" inch screen, 8MP camera, 1GB RAM, Exynos 4210 Dual processor, and 1650mAh battery.

April 2011
Release Date

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