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I’ve just bought a new hard drive and USB hub and followed all the you tube videos!!! But can’t get the iPad Air with 16.5 os to reliably recognise the Seagate drive. It worked in write only mode temporarily, but note it won’t even do that! I want to back up my files when away from the internet (on a boat). I can return the hard drive; but not sure if all hard drives will suffer the same problem???
iPad Air 3, iPadOS 16
As the iPad has limited power capabilities, dependent upon the Storage Device, an external power source is often required. For HDD or SSD, connected via USB, an external power source is almost certainly required.
If you have one of the newest iPad models, with a USB-C connector, you may need to utilise a powered USB hub (i.e., it has its own source of power) - connecting both the iPad Pro and the storage device to ports on the hub.
Some additional information can be found here:
Connect external devices or servers with Files on iPhone - Apple Support
https://www.imore.com/how-use-external-hard-drives-your-iphone-or-ipad
To be recognised by iPadOS, the attached USB storage device must be formatted to FAT, FAT32, exFAT, APFS or HFS+ with a single partition. Microsoft NTFS is not supported. Formatting and partitioning, if required, must be performed using a separate computer; iPad does not provide any facilities to format an external storage device.
When using SSD and HDD, beware of write-caching - as this has implications for connecting and disconnecting the drive without causing filesystem corruption. You should ensure that a file-write has fully completed prior to a device disconnect.
In more detail:
The type of 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, such as SSD/HDD, are a completely different proposition due to write-caching that will, for both performance and efficiency, delay completion of a file-write.
For most desktop computers, it is possible to configure an externally attached storage device either for performance (i.e., uses write-caching) 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 enabled, 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 sets a “clean switch” on the flash filesystem and signals to the computer that it is safe to disconnect.
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. iPad does not fully support devices that implement write-caching. 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 both the cause and effect, you will now understand that you can only reliably use large USB storage devices that can be configured for Quick Disconnect operation - this having major significance to non-corruption of the filesystem and reduced data throughput.
To avoid filesystem corruption that may impact usability of your SSD/HDD, the only “safe” dismount is to fully shut down the iPad before disconnecting the drive.
As the iPad has limited power capabilities, dependent upon the Storage Device, an external power source is often required. For HDD or SSD, connected via USB, an external power source is almost certainly required.
If you have one of the newest iPad models, with a USB-C connector, you may need to utilise a powered USB hub (i.e., it has its own source of power) - connecting both the iPad Pro and the storage device to ports on the hub.
Some additional information can be found here:
Connect external devices or servers with Files on iPhone - Apple Support
https://www.imore.com/how-use-external-hard-drives-your-iphone-or-ipad
To be recognised by iPadOS, the attached USB storage device must be formatted to FAT, FAT32, exFAT, APFS or HFS+ with a single partition. Microsoft NTFS is not supported. Formatting and partitioning, if required, must be performed using a separate computer; iPad does not provide any facilities to format an external storage device.
When using SSD and HDD, beware of write-caching - as this has implications for connecting and disconnecting the drive without causing filesystem corruption. You should ensure that a file-write has fully completed prior to a device disconnect.
In more detail:
The type of 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, such as SSD/HDD, are a completely different proposition due to write-caching that will, for both performance and efficiency, delay completion of a file-write.
For most desktop computers, it is possible to configure an externally attached storage device either for performance (i.e., uses write-caching) 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 enabled, 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 sets a “clean switch” on the flash filesystem and signals to the computer that it is safe to disconnect.
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. iPad does not fully support devices that implement write-caching. 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 both the cause and effect, you will now understand that you can only reliably use large USB storage devices that can be configured for Quick Disconnect operation - this having major significance to non-corruption of the filesystem and reduced data throughput.
To avoid filesystem corruption that may impact usability of your SSD/HDD, the only “safe” dismount is to fully shut down the iPad before disconnecting the drive.
Thanks for the prompt reply… I was using a USB hub…. The Seagate was powered. What else might the problem be?
If the HDD filesystem is now not recognised due to possible corruption, you may need to reformat the drive - or at least verify the filesystem - using a Windows PC or Mac computer.
Seagate 2Tb hard drive
