A-to-Zerto Glossary of Terms
Snapshots are a traditional method of backup that record and store desired data at specific points in time. Snapshots negatively impact a production environment, so they are typically only taken every few hours at most—potentially causing disastrous implications in the case of a downtime event.
What Are Snapshots ?
Traditional backup methods use snapshots to protect virtual machines (VMs). During backups, a snapshot is taken of the desired data, then it is moved to dedicated backup storage. In large organizations, this storage requires powerful resources to be able to scale and meet service-level agreement requirements. With snapshots, data gaps are a necessary evil because the snapshots deplete system resources, forcing system administrators to schedule them for low-use times (such as late at night).
Comparing closest recovery points between a snapshot and CDP after a disruption
How Snapshots Work?
Snapshots are often used to replicate Virtual Machines (VMs) from a specific point in time and to maintain multiple recovery points in order to recover from a disaster. Snapshots can be performed at the VM level or at the Storage Area Network (SAN) level.
VM level snapshots are created in the hypervisor and they incur the biggest performance impact. Any VM level snapshot-based replication system is usually configured to replicate daily or weekly, outside of working hours, to mitigate performance impact.
Storage level snapshots incur less performance impact than VM level snapshots, but still require processing power in a storage controller and at scale can still start to degrade performance. The frequency at which storage level snapshots can be created is therefore still very much limited by the potential for performance impact.
The Downsides of Snapshots
As hinted above, there are two main downsides of snapshots when it comes to backup and protection: the impacts on performance and the granularity of the points in time for recovery that they offer.
- Impact on performance. The creation and use of snapshots negatively impact the performance of the production environment, so they require careful planning and scheduling to protect data. To avoid this negative impact, snapshots are typically only taken every few hours—sometimes just once every 24 hours. Restore points that are hours apart have disastrous implications in the case of a downtime event—including up to 24 hours of data loss.
- Non-granularity. Snapshots only support per-VM consistency. This means if an application consists of multiple VMs, snapshots are unable to maintain consistency across all VMs. This could result in inconsistent recovery in case of downtime, because all VMs may be recovered to different, inconsistent points in time.
Choose Zerto over Snapshots
Snapshot technology is outdated and not an effective way to back up your data. With Zerto, you can provide more protection than snapshots with added benefits:
- Continuous backup. Zerto continuously backs up your data (with RPOs of seconds) without impacting performance.
- Granularity of seconds. Zerto allows you to recover to any point in time, just seconds apart, using journal-based recovery.