Last week-end I worked on reducing the costs of keeping backups for an extended period of time. Here is how it was:
- forgefriends virtual machines, hosted on a libvirt hypervisor, are uploaded to the cloud for backup. And kept there during a defined period of time.
The problem is that cloud storage is expensive. It is convenient when the machine crashes to reinstall them using an internet connection instead of physically going somewhere to fetch a disk. But it is less useful when looking for files that have been lost months ago: that can be done by digging into backups stored on less readily accessible backups. In order to reduce the costs while keeping backups for a long time for posterity, here is how it goes now:
- forgefriends virtual machines, hosted on a libvirt hypervisor, are uploaded to the cloud for backup and kept there during 20 days
- the backups are downloaded on a backup disk (8TB) and kept indefinitely. When the disk is full, it is replaced with a new one. At the current backup rate that’s approximately one disk a year, i.e. 200€ per year
The backup method of Enough is extremely inefficient and takes a lot of space. But it also is extremely simple which is convenient in disaster recovery scenarios: qcow2 images that are ready to boot. Although it would be nice to work on reducing disk usage while keeping disaster recovery scenarios as simple as they are, it would cost a lot more than 200€ per year.