Reduce the number of files considered for backup
CCC analyzes all of the files that are included in your backup set for consideration to be copied. If you have a particularly high number of files on your source volume, you may want to put some thought into how your files are organized. For example, if you have a large number of files that never change (perhaps some old, completed projects), you can collect these into a folder named "Archives", back it up once, then exclude it from future backups. CCC will not delete excluded items from your destination (unless you ask it to in the Advanced Settings panel), so as long as you keep the original on your source volume, you will always have two copies of your archived content. Because these items are excluded from your daily backups, CCC will not spend time or RAM enumerating through those files for changes.
Hard drive performance and interface bandwidth
Performance will be worse for smaller hard drives (e.g. physically smaller, like those in laptops), for older hard drives, and for hard drives that are nearly full and thus more likely to be fragmented. You will also get longer copy times when you have lots of small files vs. a volume filled with just a few very large files. Finally, you will see better performance with faster/more efficient interfaces -- eSata is faster than Firewire, Firewire is faster than USB (FW800 and FW400 are both faster than USB 2.0).
Spotlight Indexing
Anything that causes CCC to compete for bandwidth to your source or target volume will increase the amount of time that it takes to back up your data. Spotlight indexing is one such process that CCC typically must compete with for disk bandwidth. As you copy new data to your target volume, for example, Spotlight wants to read those "new" files so it can index their contents. Having a Spotlight index of your backup volume may be unnecessary as you probably want to search for files only on your source volume. To disable Spotlight indexing on a volume that is dedicated to backup, drag the icon of the target volume into the "Privacy" tab of Spotlight Preference Pane in the System Preferences application. If you do want the backup volume indexed, drag its icon out of the "Privacy" tab after the cloning and indexing will start immediately.
Other applications and conditions that can lead to performance problems
Over the years we have received numerous queries about poorer performance than what is expected. Careful analysis of the system log, kernel log, and Activity Monitor will usually reveal the culprit. Here are some things that we usually look for:
- Other backup software copying simultaneously to the same volume, a different volume on the same disk, or across the same interface as CCC's destination.
- Utilities that watch filesystem activity and do things when file changes are detected. Antivirus software is a common culprit, but we have also seen problems caused by other watcher applications, such as memeod and Western Digital's SmartWare.
- Did we mention Spotlight already?
- Slow interfaces — USB hubs (including the ports on a USB keyboard or display) and even some USB cables can reduce the bandwidth to your disk dramatically. We generally prefer Firewire over USB, but if you're forced to use USB, be sure that your device is plugged directly into one of the USB ports on your Mac.
- Using a wireless network connection to connect to a network volume. If you're seeing poor performance with a wireless connection, compare the performance when using a wired (ethernet) connection.
Use the Console application to view the contents of the system log and the kernel log (kernel log is only present on Snow Leopard and Lion, those messages are merged into the system log on Mountain Lion). If you're still having trouble identifying a performance problem, we're here to help.