Q: How Does The Backup Process Work For Resilient VM?

A: In general, there are 1 VM (in A machine) as production,  1 same configuration VM (in B machine) for takeover and 1 backup storage (in C machine). Everyday, the system will create a snapshot image of all the data in Production VM and store it in Backup storage. The Backup storage can store copy of images up to a certain number of days, which can be customized by each customer.

By default, a Backup storage will keep image copies of the past 14 days, which means, if today is day N since the production, the backup storage has an image copy of the Production VM data on day N; an image copy of the Production VM on day N-1; an image copy of the Production VM on day N-2; an image copy of the Production VM on day N-3; ..... an image copy of the Production VM on day N-14. If user wishes to recover the data of the Production VM on day N-8, for example, he/she can always do it from the Backup storage. 

Example: If you started to use the production VM on January 1st and customized the backup storage days up to 14, the backup process would start on January 1st as well. Then starting January 15th, disk image snapshotted from production VM 14 days earlier (i.e., January 1st) would be automatically deleted, and copied disk images from January 2nd to January 15th would still be available in the Backup storage in machine C. 

Each day, the backup process is:

• Copy disk image from Production VM (in machine A) to Backup storage (in machine C)
• Erase images on Backup storage (in machine C) earlier than 14 days
• Copy latest disk image from Backup storage (in machine C) to Resilient VM (in machine B)

Please note, the "erase images on Backup storage earlier than 14 days" does not mean erase of old data of 14 days before, because the whole data in Production VM are copied to new images and stored in Backup storage everyday. 

If one day, Production VM is down, Resilient VM will be able to replace Production VM immediately with the latest data.