Backblaze B2 Reaching “Class C Transactions Cap” with Synology NAS

Backblaze B2 Reaching “Class C Transactions Cap” with Synology NAS


You may be getting the following alerts via email.

Class C Transactions Cap Reached 100%

You have reached 100% of the free Backblaze Daily Class C Transactions Cap. To increase your Daily Class C Transactions Cap or to change your Cap Notification Settings log on to the ‘Caps & Alerts’ page

When you login to the Backblaze control panel you will see your class C transactions cap has reached.


Synology cloud sync by default does a sync check for files every 60 seconds. This uses up your daily class c translation limit (2500 daily).


You will need to increase the polling period of Synology cloud sync to prevent your backups from being halted until it is reset the next day.

  1. Open Cloud Sync from the menu
  2. Select the settings tab
  3. Change the Polling Period from 60 seconds to 3600 (1 hour)

Your backup should now run throughout the day without reaching its class C transactions cap.


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Simon Browne

Excellent article. Thank you very much. I have tried most of the other backup providers – including recently Spideroak – Excellent client and special unlimited deal caught me – but the combination of BackBlaze professionalism, the inexpensive option of B2, and Synology Cloud Sync plus your clear instructions made so much sense. Currently running a Task on the DS214 backing up family photos. 2 mirrored local disks in the Synology NAS plus 1 offsite copy of everything and MyBackup is sorted.