Eject thumb drive Apple ipad
How do I properly eject a thumb drive from my Apple air pad?
MacBook Air 13″, macOS 11.7
Question marked as
Unlike Mac and Windows PC, iOS/iPadOS does not include a safe-eject feature
Providing your attached USB Storage device does not employ write-caching (this being the case for most simple USB thumb drives) you should be able to disconnect a USB Storage device wherever the device is not being actively written to; it follows that you should ensure that a file-write has completed prior to a device disconnect.
The majority of thumb drives have an LED activity indicator. When the indicator remains OFF for several seconds, with no indication of activity, it is usually safe to disconnect without risk of corruption.
In more detail:
The type of USB storage device that you are using will have significant impact on “safe dismount” from your iPad. Simple flash storage devices can be dismounted provided that an active write isn’t occurring. More complex devices, that employ write-caching, are a completely different proposition…
Write-caching is a feature of more complex SSD and other bulk storage devices.
For most desktop computers, it is possible to configure an externally attached storage device either for performance (i.e., uses write-caching - where available) or for Quick Removal. This determines how and when information is “written” to non-volatile storage.
When configured for Quick Removal, information from the host computer is written immediately to the storage medium. This has the advantage that you may disconnect the storage device from the host computer, without risk of corrupting the file-system, at any time that data is not being actively transmitted to the storage device. Whilst being a completely valid and useful method of managing data storage, for reasons beyond the immediate scope of this description, this method is less efficient and slower.
Alternatively, when write-caching is used, information from the host computer is “cached” in separate (high performance) volatile storage within the storage device - and when sufficient information has been received, a “block” of data is written in single write-cycle. Whilst being faster and more efficient, this method comes with the penalty of the host computer having to notify the storage device of a impending device-disconnection before it is disconnected. This warning ensures that the storage device will flush any pending data from its volatile cache-memory to non-volatile storage - and in so doing both sets a “clean switch” on the flash filesystem and signals to the computer that it is safe to disconnect. Intended disconnection by the User is notified using the Safe Disconnect feature - however, this mechanism is not available for iOS/iPadOS devices.
A drive configured for write-caching, upon connection to a host computer, is checked for the “clean switch”; if present, the storage device is “mounted” and made available to the operating system. By contrast, if the “clean switch” is not detected (this will occur if the storage device was disconnected prior to being notified of a “dismount”), the filesystem must be assumed to be potentially corrupt; pending data within the write-cache may not have been written to the drive.
So, the relevance of this to iPad is simple. While iPad supports devices that implement write-caching, you must be mindful of how and when you disconnect the storage device from the iPad. iPadOS lacks the ability to inform the storage device of imminent disconnection of the storage device from the USB bus. iPad also lacks capability to detect and scan/repair corrupt storage devices.
In summary, now that you [hopefully] understand the technical differences between storage devices that employ write caching - and those that don't. For storage devices that use write-caching, the only “safe” dismount is to fully shut down the iPad before disconnecting - whereas simple thumb drives can be disconnected whenever an active write is not taking place.
