"System" takes up 14+ GB of device storage, continues to grow

Number:rdar://33956346 Date Originated:August 17, 2017
Status:Closed Resolved:October 23, 2017
Product:iOS + SDK Product Version:11.0
Classification:Other Reproducible:Always
Starting with iOS 11 beta 4, the "System" now takes up anywhere from 14.0 GB to 19 or more GB of storage space, as reported by the device's storage statistics in the Settings app. As more storage space is made free / available to the device (i.e. by deleting apps, videos, etc.) the "System" begins to take up more room - its as if its literally eating the available free space on the device. For example, after updating to iOS 11.0 beta 6, a device may initially have a "System" item taking up ~14 GB, but after a day or two and the deletion of a few items, "System" may have grown to 16 GB or even 18 GB. This process continues until the device thinks it is out of storage space and can no longer update apps, sync to iCloud, or take photos.

Steps to Reproduce:
1. Update to a recent iOS 11 beta (happens on at least 4, 5, and 6) on a 32 GB iPhone using very little storage space (i.e. the device has a relatively small photo library, some music, and a few apps)
2. Open Settings and navigate to "iPhone Storage" in the "General" section
3. Wait for storage calculations to complete.
4. The storage bar graph visualization at the top of the table view will show the different items taking up space and a large gray section for "System".
5. Scroll down to the bottom of the list. "System" will be listed as taking up anywhere between 14 GB to 19 GB (possibly more, although not yet seen in tests).
6. Exit the Settings app.
7. Delete some content from the device and wait a few moments, then return to the "iPhone Storage" section of the Settings app.
8. The "System" size will have increased after deleting content from the device.
9. Exit the Settings app.
10. Use the device normally over the course of a day or two, then return to the "iPhone Storage" section of the Settings app.
11. The "System" size will have increased even further, and without any significant changes to the system or to the device.

Expected Results:
The device's operating system should take up a relatively small amount of space; 14 to 19 GB of system storage on a 32 GB device is insanity (let a lone the poor souls with 16 GB devices).

The device's operating system should not randomly grow in size or eat available free space.

Even if the OS is randomly "growing" or claiming chunks of storage space, this space should be able to be reclaimed, or purged, by other processes.

Observed Results:
The device's operating system takes up anywhere from 14 to 19 GB of system storage on a 32 GB device.

The device's operating system randomly grows in size, eating any available free space. This newly claimed storage space is non-purgeable and can only be reclaimed by restoring the device via iTunes. OTA Software Updates also do not reclaim the space. Furthermore, even after a restore via iTunes, the same issue recurs and available space begins to diminish.

iOS 11.0 (15A5354b)

Seems that this problem is happening on other devices as well (https://forums.developer.apple.com/thread/84466).

Would like to take a sysdiagnose, but this issue is chronic and not necessarily triggered by any single action that a sysdiagnose would pick up within the ten minute window.


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