Why are there slow transfer rates or long backup times?

Sometimes the backup time estimates seem like a surprisingly long amount of time - hours, days, or even weeks. This article will help explain possible reasons for the long backup time and steps you can take to reduce it if needed. 


Reasons for long backup time estimates

This is your first backup - Your initial backup will take much longer than later backups, since only new or changed files will be uploaded in later backups. If you are backing up a large library of music, pictures, or videos, your first backup may take several hours or days. Don't worry! Your later backups will likely only take a few minutes based on the amount of new and changed files.

Slow upload speeds - Most Internet connections (Cable, DSL, etc.) are designed to have a much lower upload speed than your advertised download speeds. For example, a typical cable Internet connection advertised at 5Mbps will likely only have an upload speed of 512-768Kbps, and backups occur at the slower upload rate. The good news is that if you ever need to restore your files, it will be much faster—usually 10 times faster than your backup! You can test your actual upload and download rates by visiting: http://www.speedtest.net

Backing up too much data - While your first instinct may be that you want to back up your entire hard drive, that is typically not the best option for online backup. Much of the data on your hard drive is operating system and application files that can easily be re-installed from CD if your computer were to crash. Backing up this extra data will simply cause your backups to take longer and result in higher storage costs. Instead, you should focus on backing up your irreplaceable files—your documents, photos, music, movies, and program data that cannot simply be reinstalled if lost.

Lots of small files - Because there is a fixed time overhead required to back up each individual file, if you are backing up large amounts of small files, it will take longer than a smaller number of big files. You may only be able to achieve a fraction of your maximum upload rate if you are primarily backing up small files. While your initial upload may take much longer, later uploads should still be relatively fast as only the new or changed files will be uploaded.

 Exceeding the network drive cache size - This only applies if you are manually uploading data via the network drive, not if you are using the automatic backup feature. When using the network drive, data is initially copied into a local cache then uploaded to your online disk. If the local cache fills up, the incoming file data from the operating system will slow down until space can be freed in the cache by uploading data over the network. This isn't slowing down your actual upload, but you may see a slow transfer rate for data being copied into the cache. The default cache size is 1GB and can be adjusted in the Network Drive settings.


Steps to reduce the impact of long backups

If you have a backup that is going to take several hours or days to complete, there are several steps you can take to reduce the impact of using your entire upload bandwidth during that time.

Enable Bandwidth Limiting - The bandwidth limiting option in the Configuration dialog allows you to control bandwidth. You can even set a time period to enforce the bandwidth limit. While setting a bandwidth limit may actually increase your backup time, it can reduce the impact it has on other network activity like web browsing and downloads.

Automatically stop the backup after a period of time - Under the backup Schedule settings, you can automatically stop the backup if it runs over a certain number of hours. The backup will start again where it left off at the next scheduled time. This can allow you to run your initial backup over several nights, while having it automatically stop before you start using the computer in the morning.

Exit the Activity Monitor application - On Windows and Mac, your backup will continue in the background. You can always restart the monitor to see where you are or if there were any errors, but sometimes it is best to leave it "out of sight" until the initial backup is over.

Estimating backup times - It is sometimes surprising how long it takes for an initial backup.  Note: Transfer rates are in kbps (kilobits per second) not kilobytes. Here is an example of a typical backup:

  • Backup Files: 10 Gigabytes
  • Upload Speed: 512 kbps

You can calculate the number of seconds required roughly as: (10 GB * 1000000000 bytes * 8 bits/byte)  / 512000 bps = 156250 seconds

Backup time = 156250 seconds or ~ 2 days

As you can see, an initial backup can take some time; however, future backups will be much shorter as only changed data needs to be uploaded.



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