Open Radar

 
Summary:
Safari fails to download large files (approx > 2Gb) when time machine is active if the time machine backup disk is disconnected.

Steps to Reproduce:
0) Enable Time Machine to a USB backup disk. Disconnect backup volume.

1) Download a large file using Safari. I used XCode6-Beta2 as a test file, which is 2.43Gb, to reproduce the problem. I’m uncertain of the exact size threshold, but 2Gb seems suspicious.

Expected Results:
Safari downloads the file in question.

Actual Results:
Safari downloads the entire file, then fails to move it from the .download bundle to the target file. If the .download bundle is opened with “Show Package Contents”, the target file is present, and passes a DMG checksum test (so it has been completely downloaded).

The error Safari presents to the user within the downloads popover is:
“Cannot write file”

The error logged to the sandbox is more informative:
Jun 30 03:28:59 X.local sandboxd[146] ([6127]): com.apple.WebKit(6127) deny file-write* /.MobileBackups/Computer/2014-06-30-031846/Volume/Users/tim/Downloads/xcode_6_beta_2.dmg.download/xcode_6_beta_2.dmg

Now attach the Time Machine backup drive and repeat the download. This time it works correctly.

Version:
Safari Version 7.0.4 (9537.76.4) running on OS X 10.9.3 (13D65)

Notes:
This problem manifests in Safari, but may in fact be a sandbox bug in OSX.

Update: 10th July 2014 - Closed as duplicate of 15066646