Article ID: kb00108Last Modified: 09-Oct-2026

How to Increase Upload Speed

For backup duties, the data transmission speed is a key performance indicator. CloudBerry Backup provides users with efficient data transmission tools, but in some cases, backup processes can be slowed down. This article guides you through backup speed slowdown issues and the measures that help to avoid them.

Antivirus Software and Firewall

Most Windows users (less relevant for macOS users) use firewall and antivirus software. In some cases, firewalls and antivirus applications can slow down data transfers by limiting bandwidth and preventing long-time data transfers. At first, check if CloudBerry Backup is included in the allowlist in your firewall and antivirus software:

  • The following executable files must be in the allowlist:
    • CloudBerry Backup.exe
    • CBBackupPlan.exe
    • Cloud.Backup.Scheduler.exe
    • cbb.exe

See the list of allowed TCP ports (for both outgoing and incoming connections) for any firewall or antivirus.

TCP ports:

  • 80
  • 443

Protocols:

  • TLS 1.2 (requires Microsoft .NET Framework 4.5 installed)

The Microsoft .NET Framework 4.5 can be installed on instances running Windows 7 or later. If Microsoft .NET Framework 4.5 cannot be installed, consider using offline product activation.

Fine-Tuning Backup Settings

Chunk Size

CloudBerry Backup splits files into 10 MB chunks by default to upload them to storage. The chunk size is adjustable. The overall backup performance can be improved by adjusting the chunk size so that it is equal to the file size, as shown in the diagram below.

In fact, this is a heuristic value, as the chunk size (or N x chunk) must fit approximately 70% of files. Thus, the backup will not have many small chunks; e.g., 21.5 MB cannot be split efficiently to 7 MB chunks.

For example, if the average size of a single file of your backup plan is 17 MB, you should adjust the chunk size to 18 MB to optimize the process. However, consider the recommendations of point 2.

For backup plans containing smaller files, you can use small chunks; accordingly, it is recommended to use large chunks for large files.

Mind that the RAM consumption may grow significantly in accordance with the formula below: RAM consumed = 2 x thread count x chunk size

The principles of network connection are also a thing to consider.

For a Gigabit connection, a 10 MB chunk size could be too small (provided it is not set because the files are very small), so it is recommended to set it to 120 MB or similar.

If you are using a modem connection (satellite or cellular), then the minimum chunk size of 5 MB is recommended.

Note that your host connection bandwidth is likely to be used by multiple processes on multiple machines. So, instead of theoretically possible bandwidth, it is reasonable to use the expected available bandwidth for upload speed estimation.

Thread Number

CloudBerry Backup uploads data to the cloud storage in multiple parallel upload threads (if the storage supports multiple thread uploading).

It is important to adjust the thread number to use network bandwidth and CPU most effectively: too many threads may create a significant load for both network and CPU and decrease overall performance. Too few threads will reduce the upload speed.

If a network connection is not stable, smaller chunks and smaller thread count work better. For small file backups, a bigger number of threads and smaller chunks will be more efficient. For big files and middle-sized files, it is recommended to use the default number of threads (6 in Backup for Windows, 5 in Backup for Linux and Mac) and chunk size adjusted as described in the paragraph above.

Mind Your Backup Contents

To improve overall performance, it is reasonable to exclude files of smaller importance from your backup plan (or include important files only). Use backup filters to manage your backup content.

This may differ slightly on different operating systems. See the example of using file filters for macOS GUI in the figure below.

Advanced Filters as a step of backup plan wizard

One more option is splitting the whole dataset into several backup plans.

For example, images and videos do not change frequently, so they can be backed up on a monthly basis.

On the contrary, MS Office documents may change several times a day, so they can be scheduled for a daily backup plan [ *doc; *docx ] files.

In addition, you might never want to back up any temporary files. Thus, exclude (or don't include) all [ *tmp; temp; ~; *.bak ] files from all plans.

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