Avast Mac Security Causes Massive Increase in Dropbox Sync Times on AFS

Avast Mac Security
1

With macOS 10.13 (High Sierra), Apple has begun the transition from the Mac’s old file system (HFS+) to its new one (AFS). Right now, when a user upgrades to 10.13, if the Mac has an SSD internal drive (as most newer Macs do), it is automatically upgraded to AFS. Over time Apple intends to move all users to the new file system.

I’ve run tests on multiple machines and the results are consistent: While Avast Mac Security works fine with Dropbox folders on HFS+ volumes, it radically increases sync times when a Dropbox folder is located on an AFS volume.

With a small Dropbox this may not be very noticeable, but with a medium-to-larger one, it has a huge negative impact. For example, I have a Dropbox that’s approximately 60GB with 90K files. With Avast running, on an HFS+ volume, full sync (the one that happens right after Dropbox starts up, and sometimes at other points in time) time is about a minute. With the folder on an AFS volume, however, full sync time jumps to 16 minutes!

As soon as I turn off Avast’s file shield, full sync time drops back to a minute.

This is a huge problem for Dropbox users, and it’s going to get worse as more Mac users migrate to AFS. Are Avast developers aware of it?

Thanks.

2

Hello,
thank you for your report, we are not aware of it and this certainly begs for investigation. Could you please provide few more clarifications?

  1. We are talking about APFS?
  2. In your comparison of dropbox on HFS+ vs APFS, were both done on 10.13 or HFS+ was done on 10.12 before the migration?
  3. I assume the synchronization does not actually do any downloads, only checks that nothing has changed?
  4. Which version of Avast are you using?
    Kind regards,
    Ondrej Kolacek
3

  1. You’re correct–APFS. I mistakenly thought it was abbreviated AFS.

  2. I upgraded two machines from 10.12 to 10.13. One of the machines had both an SSD and a mechanical drive, the other only an SSD. All 3 drives had large Dropbox folders. The SSD’s were automatically upgraded to APFS during the 10.13 upgrade.

On 10.12 (all HFS+), no sync time problems with any of the Dropbox folders.

On 10.13, both Dropbox folders on the APFS-upgraded SSD’s exhibited the long sync time problem. The Dropbox folder on the mechanical drive, which was still HFS+, didn’t have any increase in sync time vs. pre-upgrade.

  1. You’re mostly correct. There are some reasons file uploads or downloads might take place during a startup sync. But the vast majority of the time is spent doing what Dropbox calls “indexing”.

  2. Avast version 13.3.

Thanks.

Bob

4

To close the loop here, Avast (ondrej.kolacek) has been able to duplicate the issue, and traced it to a bug in Dropbox that results in Avast (on High Sierra APFS volumes only) doing a scan of every file in the Dropbox folder. Avast is contacting Dropbox about the issue, and will build a workaround for it if necessary in a future release.