Troubleshooting slow performance when copying files to or from a network volume

Product: 
ccc6

Network performance is usually the bottleneck of a backup task that copies files to or from a network volume, but there are several other factors that can affect performance as well. Here are some suggestions for improving the performance of your NAS-based backups.

"The task was aborted because a subtask did not complete in a reasonable amount of time"

Product: 
ccc6

Occasionally a backup task can stall if the source or destination stops responding. To avoid waiting indefinitely for a filesystem to start responding again, CCC has a "watchdog" mechanism that it uses to determine if its file copying utility has encountered such a stall. By default, CCC imposes a ten minute timeout on this utility. If ten minutes pass without hearing from the file copying utility, CCC will collect some diagnostics information, then stop the backup task. Our support team can analyze this diagnostic information to determine what led to the stall.

Finder or App Store finds other versions of applications on the backup volume

Product: 
ccc6

Occasionally we receive reports of odd system behavior, such as:

"CCC found multiple volumes with the same Universally Unique Identifier"

Product: 
ccc6

Occasionally a circumstance arises in which CCC presents the following error message before creating or running a backup task:

Antivirus software may interfere with a backup

Product: 
ccc6

Some antivirus applications may prevent CCC from reading certain files, mounting or unmounting disk image files, or, in general, degrade the performance of your backup. In some cases, antivirus applications can even affect the modification date of files that CCC has copied, which will cause CCC to recopy those files every time as if they have substantively changed. In another case, we have seen such software create massive cache files on the startup disk during a backup, so much so that the startup disk became full.

Coping with errors caused by APFS filesystem corruption

Product: 
ccc5

We regularly see cases of APFS filesystem corruption that lead to errors during a backup task. This corruption is typically presented in an error like one of these:

readlink_stat("/Photos/Foo/2020_Dumpster_fire.jpg") failed: Illegal byte sequence (92)
rename("/Photos/Foo/.2020_Dumpster_fire_out_of_control.jpg.asdfgh" -> "/Photos/Foo/2020_Dumpster_fire_out_of_control.jpg") failed: No such file or directory (2)

When CCC encounters these errors, the affected items are listed in CCC's Task History window, often with this overly-optimistic advice:

macOS Big Sur Known Issues

Product: 
ccc5

Some Big Sur startup volumes don't appear in the Startup Disk Preference Pane

In the past, the Startup Disk Preference Pane would list all available startup volumes, including volumes cloned by CCC (whether CCC used ASR or its own file copier). Some Big Sur cloned volumes do not appear in the Startup Disk Preference Pane, despite being perfectly bootable.

We have reported this issue to Apple (FB8889774) and we are currently awaiting a response.

Problemen met APFS-replicatie oplossen

Product: 
ccc5

De APFS-replicator van Apple werkt doorgaans snel en foutloos maar ondervindt problemen in sommige gevallen (of werkt helemaal niet). CCC werkt om zo veel mogelijk van deze teleurstellende resultaten te vermijden maar we hebben de volgende aanbevelingen als de APFS-replicator van Apple het laat afweten.

Some third-party storage drivers may cause hardware misbehavior

Product: 
ccc5

We occasionally receive reports of strange behavior from USB devices, e.g. slow performance, disks dropping offline in the middle of the backup task. In some of those cases we've discovered that third-party storage drivers are causing the problem. In particular, the SAT-SMART drivers and some ancient BlackBerry USB drivers can lead to problems. If you're troubleshooting a USB device behavior or performance problem, we recommend that you consider uninstalling these drivers.

macOS Catalina Known Issues

Product: 
ccc5

Apple introduced a bug in 10.15.5 that prevents the creation of firmlinks

The chflags system call no longer works correctly on 10.15.5 with regard to setting the special "firmlink" flag that establishes links between the System and Data volume group members. If you're establishing a new backup of macOS 10.15.5 or later, CCC 5.1.17 (and earlier) will be unable to create a correctly-functioning APFS volume group. Many folders on the destination volume will appear empty, and the volume will not be bootable.