Snapshots and backup are popular ways to secure digital assets, and although both methods seem to “copy” data, they are not the same. Treating snapshots as backups is a costly, cumbersome process and potentially puts your data at high risk.
Let’s understand the difference between snapshots and backups to improve data security and reliability.
What is the difference between snapshots and backups?
The main difference between snapshots and backups is that the latter is isolated from the mainframe. That means snapshot copies are stored on the original network, unlike backup copies. Snapshots work well for frequent protection measured in minutes or hours while backups are used for regular protection.
What is a snapshot?
A snapshot is an image of your system/volume at a specific point in time. The first snapshot is an exact copy of the given data volume. Subsequent snapshots store data blocks that have been changed or added, enabling quicker versioning. In other words, snapshots are a point-in-time recovery that protects data against incidents like hardware failure or data corruption.
What are snapshots used for?
Snapshots are used for version control to mitigate any potential damage to the system before upgrades, changing installed software, uninstalling components, etc. Therefore, snapshots are extensively used for development and testing purposes because they help recover recently modified data.
How do snapshots work?
A snapshot creates files with extensions. These files are placed on the same storage infrastructure as the host system. For example:
.vmdk file: A virtual disk file that contains the raw data in the base disk.
delta.vmdk file: An incremental disk, represented in the format of a .00000x.vmdk file, that captures all changes between the current state of the virtual disk and the last snapshot taken.
vmsd file: A centralized file containing snapshot information and metadata. Snapshot managers regard this file as their primary source of information.
.vmsn file: The snapshot state file that stores the current configuration and optionally the running state of a virtual machine (VM). It allows you to revert to a running state of the VM.
What are the different types of snapshots?
Although the execution of a data snapshot varies from vendor to vendor, there are a few popular techniques that create and integrate snapshots.
Copy-on-write
The copy-on-write snapshot includes metadata that describes the data blocks that have changed (copies on writes) since it was created. Since copy-on-write snapshots do not create a copy of the metadata, they are almost instant. However, they are performance-intensive since they require three I/O operations for each write: one read and two writes.
Redirect-on-write
Redirect-on-write snapshots use pointers to reference snapshot-protected blocks, meaning the original copy contains the point-in-time snapshot data while the altered data is saved to the snapshot storage. This consumes fewer performance resources since each modified block generates a single write IO. However, in the event a snapshot is deleted, reconciliation between multiple new blocks and the original block becomes complex and confusing.
Continuous data protection (CDP)
CDP snapshots are created in real-time, which means every time a change is made, the snapshot of the original copy is updated. It enables continuous capturing and tracking of data modifications, automatically saving every version of the data that the user creates locally or at a target repository. However, regular snapshot creation and updates eat into network performance and bandwidth.
Clone/mirroring
A clone/mirror is related to snapshots but is entirely different in terms of mechanism. It is an identical copy of the entire volume of storage, not just snapshots of updated data. Easy data recovery, replication and archiving as the entire volume remains available even if the primary/original copy is lost. However, saving such large data volumes makes the process slow and requires huge storage space.
What are the pros and cons of snapshots?
Snapshots come with their fair share of advantages and disadvantages.
Here are some of them:
Pros
- Faster rollback to a previous point in time as compared to backups
- Created quickly and easily without any impact on the production server
- Eliminates the need for Windows native backup solutions, reducing the total cost of ownership (TCO)
Cons
- Vulnerable to disruptions that affect the production server
- Consumes a large chunk of the primary storage capacity
- Lacks granularity — you must recover data in its entirety since individual files cannot be restored from snapshots
What is backup?
Techopedia defines data backup as the process of duplicating data to allow retrieval of the duplicate set after a data loss event caused by natural disasters, human error or cyberthreats like ransomware.
What are backups used for?
Backups are perfect for long-term data storage since they are not designed to override each other. Ideally, backups should be used to restore old backup files, mitigate the potential risk of data corruption, enable point-in-time recovery, etc. A good investment in backups ensures business continuity.
What are the different types of backups?
Not all backup systems are the same. Choose the backup type that addresses your data security needs. Pick the right type of backup and make the smart move.
Full
A full backup involves the creation of a complete copy of an organization’s files, folders, SaaS data and hard drives. Essentially, all the data is backed up into a single version and moved to a storage device.
Differential
Differential backup falls between full backup and incremental backup. It involves backing up files, folders and hard drives that were created or changed since the last full backup (compared to just the changes since the last incremental backup).
Incremental
Incremental backup involves backing up all the files, folders, SaaS data and hard drives that have changed since the last backup activity. It could be the most recent full backup in the chain or the last incremental backup.
How do backups work?
A backup strategy applies to critical databases or related line-of-business applications. The strategy works within a framework of predefined policies, which includes establishing recovery objectives (RTO and RPO) for each data source and application. A good backup strategy generally involves scheduling a full backup recurring at least once a week, followed by a series of differential or incremental backups.
What are the pros and cons of backups?
Backups are complex and come with their own pros and cons.
Pros
- Cost-effective since it does not need significant investment in staff, infrastructure or setup
- Provides an advanced level of security by storing data off-site
- Enables you to easily scale up and down depending on the storage volume you need
Cons
- Backing up big data can take more time due to high dependency on network connectivity
- Unorganized backup file access management increases security risks and data corruption
- Poor host performance and app availability due to data latency and bandwidth issues
Snapshots vs. backups: Summarized
| Snapshots | vs. | Backups |
|---|---|---|
| Stored in the same location where original data is present | Storage | Stored in another location, same server or the same drive |
| Relies on dependent files for restoration | Restore | Independent and self-contained files that do not require cross-file dependencies to restore |
| Snapshots are useful for development and testing purposes | Use cases | Long-term protection of digital assets |
| Point-in-time copy of your object metadata | Function | Complete replica of your database |
| Takes less time to copy data | Duration | Takes more time to copy data |
| Less storage space | Storage | More storage space |
| High security risks | Security | Low security risks |
Complete data protection with Unitrends
Unified BCDR empowers users to back up files, images, applications and host-level machines (based on VM snapshots) while delivering advanced recovery features that go beyond the native capabilities of snapshots. It includes granular item recovery, instant recovery for VMs and Windows servers, deduplication, encryption, automated application-level recovery testing and more.
Learn more about how Unitrends helps you achieve robust data protection with the agility to support all workloads with our guide Selecting the Right Backup Deployment.