updated 02:10 pm EST, Sat November 19, 2011
Galaxy Nexus follows iOS model of unified storage
Google engineer Dan Morrill in a discussion on Reddit explained the Galaxy Nexus' lack of USB Mass Storage mode in terms closer to those used for the iPhone. Since using the technique requires a space dedicated solely to storage, like a microSD card slot, it wouldn't have been possible to implement USB Mass Storage or the card slot while making the entire device's storage space available to any content, whether an app or music. Google also wanted to eliminate the need for a file manager, instead taking an iOS-like direction where users don't have to think about where content is stored; both USB Mass Storage and a microSD slot would have forced that, he said.
"There's no particular hardware reason a device can't have both [large internal storage and USB/microSD]," Morrill said. "The problem is that there is no good UI for it. One of the core Android principles is that you never need a file manager. Ever. We wanted to avoid the obnoxious 'sneeze and a file picker appears' syndrome of basically every other OS [except iOS]. Local data that apps know how to handle should just be magically available within the apps, or stored in the cloud. You shouldn't have to go spelunking on your SD card to find data."
On the Galaxy Nexus, going with unified storage also meant Google and Samsung weren't limited to the FAT32 file system, which both caps the maximum amount of storage and prevents Google from using more advanced features that come with newer file systems, like ext3. "We got tired of seeing OEMs include many [gigabytes] of internal storage for music, while users were still running out of space for apps and data," Morrill said.
The Android team member did stress that Android 4.0 supports USB Mass Storage outside of the Galaxy Nexus, but that any device that does is likely to have just a small amount of built-in space and encounter similar problems as before, where storage wasn't seamless depending on the app or content. The company was "thinking about compromises" to get some of the advantages of a card slot and USB mass storage, he said. One example might be a slot that prompts users either to import or export content when a card is inserted, much like the camera adapter for iOS devices, or else a migration tool to permanently transfer content over to a larger card.
Although not directly referencing Apple, the commentary helps partly explain the inability to mount an iOS device as a drive in the OS and the lack of built-in card slots. Doing either could potentially lead to compromises in how Apple manages its file system, which is closer to its Mac OS X roots, as well as to having to introduce complexity and possible confusion to the interface and app management. A 64GB iPhone 4S costs more than it would to get an equivalent Android 2.3 phone with a microSDHC card bringing it to that storage, but only Apple of the two can guarantee that the user will have unbroken access to all of that space.
The limitation on the Galaxy Nexus may nonetheless frustrate some owners in the US. Verizon's model is expected to stop at 16GB of internal space and will neither have a card slot to expand or offload data nor a raw USB connection to move files on or off. It does support Media Transfer Protocol (MTP) and Picture Transfer Protocol (PTP) to sync music and photos, but these also reduce proper support on Linux and Macs, which ironically are used much more often at Google than Windows.