Resolución de problemas

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:

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.

La herramienta de replicación APFS de Apple normalmente es rápida y funciona a la perfección, pero no puede gestionar ciertas condiciones de forma elegante (o de ningún otro modo). CCC intenta evitar la mayor cantidad de estos resultados poco elegantes, pero tenemos las siguientes recomendaciones para los casos en los que el replicador APFS de Apple falla.

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.

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.

Update November 2020: Apple has resolved this Finder bug in macOS Big Sur.

CCC solo copiará los elementos que difieran entre el origen y el destino. De este modo, si finaliza una tarea de copia de seguridad y la vuelve a ejecutar al día siguiente, CCC únicamente copiará los elementos que se crearon o modificaron después de ejecutarse por última vez la tarea de copia de seguridad. CCC determina si un archivo ha cambiado usando su tamaño y su fecha de modificación. Si el tamaño de un archivo o su fecha de modificación son distintos en el origen y el destino, CCC copiará ese archivo al destino.

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.

Occasionally a backup task can stall if the source or destination stops responding. To avoid waiting indefinitely for a filesystem to start responding again, Carbon Copy Cloner 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.

Por omisión, CCC empieza con un límite del borrado de SafetyNet que creará 25GB de espacio libre en el destino al inicio de cada tarea de copia de seguridad. CCC aumentará ese límite automáticamente según sea necesario. Si usa las opciones predeterminadas de SafetyNet en CCC y se encuentra con el error «el destino está lleno», puede que tenga que aplicar un límite de borrado más liberal en Ajustes avanzados. La cantidad de espacio libre necesario en el destino depende del tamaño de los archivos que suele editar a lo largo del día.