The rule goes as follows: keep three copies of your data, two on different storage mediums, and one located off-site. We recommend the 3-2-1 rule, which is a common industry approach to backing up data from any failure scenario. Mission-critical data should always be backed up to a separate location.
I know I've said it already but I want to reiterate, snapshots are not adequate backup. It should be noted, however, in case of, let's say a large-scale disaster or damage of the source data, the snapshot may become lost. This is why snapshots can be an absolute godsend in situations like these. The name of the game in today's fast-paced business environments is availability, and companies need to be able to recover from mistakes made where loss of data occurs with minimal or no downtime. So ZFS snapshots definitely come in handy for system admins who may have some “accident-prone” users that may end up misplacing or losing very important files.Īlthough ZFS snapshots serve a purpose and they serve them well, don't be fooled into thinking that they in any way replace an adequate backup solution. One useful feature for ZFS snapshots is the ability to mount them read-only to allow for recovery of files or to rollback an entire file system to the last time a snapshot was created. It's for this reason that you will want to continuously create new snapshots and remove old ones on a specific schedule that makes sense for your use case, otherwise you may end up with some extremely large snapshots. However, depending on your use case, this may vary.
It's for this reason that you may want to continuously add new snapshots and delete old ones as time goes by. So a ZFS snapshot will continue to grow in size as data gets added to the live file system. And then once that write completes, the metadata is then updated to point to the new location. Unlike other traditional file systems, when data is overwritten in ZFS, the data is written to a new block, rather than overwriting the old data in its place. So a ZFS snapshot is a copy of a data-set or a volume that takes up nearly zero space and can be created almost instantly due to the way ZFS works with its copy-on-write system.
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