Data Backup And Data Snapshot Difference
In computer systems, a snapshot is the state of a system at a particular point in time. The term was coined as an analogy to that in photography. It can refer to an actual copy of the state of a system or to a capability provided by certain systems.

Rationale[edit]
A full backup of a large data set may take a long time to complete. On multi-tasking or multi-user systems, there may be writes to that data while it is being backed up. This prevents the backup from being atomic and introduces a version skew that may result in data corruption. For example, if a user moves a file into a directory that has already been backed up, then that file would be completely missing on the backup media, since the backup operation had already taken place before the addition of the file. Version skew may also cause corruption with files which change their size or contents underfoot while being read.

One approach to safely backing up live data is to temporarily disable write access to data during the backup, either by stopping the accessing applications or by using the lockingAPI provided by the operating system to enforce exclusive read access. This is tolerable for low-availability systems (on desktop computers and small workgroup servers, on which regular downtime is acceptable). High-availability 24/7 systems, however, cannot bear service stoppages.
Snapshot Data Backup; Data Backup And Data Snapshot Difference Windows 10; Snapshot Vs Backup; The Main Difference: The Technology Most traditional backup solutions are what we call file-level recovery solutions, which means that they function by going into your servers and copying all of your files (or files that have changed) to a backup. One of the common abuse of language in Virtualisation is the use of the term snapshot to designate a backup.Let me explain the fundamental difference between a virtual machine snapshot and backup. Virtual machine snapshot. Both VMware and Hyper-V snapshots capture the state (eg. Powered-on, powered-off, suspended), data. In the event of data loss or a ransomware attack, restoration of the data, site structure, and permissions can be a long, and sometimes manual process — unless your data has been backed up. Backup: Data Recovery. When it comes to recovering data, there are marked differences between sync and share services and backup recovery. Otava continues its business continuity series of videos on data backup and replication by explaining the difference between a snapshot and a full data backup. Steven: The difference between a snapshot and a backup: A snapshot is, think about it as a Polaroid picture. What Is the Difference Between AWS Snapshot and Backup? Ever-increasing amounts of business-critical data, particularly in virtualized environments and in the cloud, have shaped the need for reliable data protection technologies.
To avoid downtime, high-availability systems may instead perform the backup on a snapshot—a read-only copy of the data set frozen at a point in time—and allow applications to continue writing to their data. Most snapshot implementations are efficient and can create snapshots in O(1). In other words, the time and I/O needed to create the snapshot does not increase with the size of the data set; by contrast, the time and I/O required for a direct backup is proportional to the size of the data set. In some systems once the initial snapshot is taken of a data set, subsequent snapshots copy the changed data only, and use a system of pointers to reference the initial snapshot. This method of pointer-based snapshots consumes less disk capacity than if the data set was repeatedly cloned.
Implementations[edit]
Volume managers[edit]
Some Unix systems have snapshot-capable logical volume managers. These implement copy-on-write on entire block devices by copying changed blocks—just before they are to be overwritten within 'parent' volumes—to other storage, thus preserving a self-consistent past image of the block device. Filesystems on such snapshot images can later be mounted as if they were on a read-only media.
Some volume managers also allow creation of writable snapshots, extending the copy-on-write approach by disassociating any blocks modified within the snapshot from their 'parent' blocks in the original volume. Such a scheme could be also described as performing additional copy-on-write operations triggered by the writes to snapshots.
On Linux, Logical Volume Manager (LVM) allows creation of both read-only and read-write snapshots. Writable snapshots were introduced with the LVM version 2 (LVM2).[1]
File systems[edit]
Some file systems, such as WAFL,[note 1]fossil for Plan 9 from Bell Labs, and ODS-5, internally track old versions of files and make snapshots available through a special namespace. Others, like UFS2, provide an operating system API for accessing file histories. In NTFS, access to snapshots is provided by the Volume Shadow-copying Service (VSS) in Windows XP and Windows Server 2003 and Shadow Copy in Windows Vista. Melio FS provides snapshots via the same VSS interface for shared storage.[2] Snapshots have also been available in the NSS (Novell Storage Services) file system on NetWare since version 4.11, and more recently on Linux platforms in the Open Enterprise Server product.
EMC's Isilon OneFS clustered storage platform implements a single scalable file system that supports read-only snapshots at the file or directory level. Any file or directory within the file system can be snapshotted and the system will implement a copy-on-write or point-in-time snapshot dynamically based on which method is determined to be optimal for the system.
On Linux, the Btrfs and OCFS2 file systems support creating snapshots (cloning) of individual files. Additionally, Btrfs also supports the creation of snapshots of subvolumes. On AIX, JFS2 also support snapshots.
Sun MicrosystemsZFS has a hybrid implementation which tracks read-write snapshots at the block level, but makes branched file sets nameable to user applications as 'clones'.
Time Machine, included in Apple's Mac OS X v10.5operating system, is not a snapshotting scheme but a system-level incremental backup service: it merely watches mounted volumes for changes and copies changed files periodically to a specially-designated volume using hard links.[note 2] This is because the HFS Plus file system does not have a snapshotting feature; Apple's new APFS file system introduces such a feature.
Operating systems[edit]
The Phantom OS is based on a snapshot concept, saving the state of all applications by design.
See also[edit]
Notes[edit]
- ^WAFL is not a file system. WAFL is a file layout that provides mechanisms that enable a variety of file systems and technologies that want to access disk blocks.
- ^Time Machine is not a file system and it does not make use of a snapshotting feature. It is only included here as a reference.
References[edit]
- ^'LVM HOWTO'. 3.8. Snapshots. tldp.org. Retrieved 2013-09-29.
- ^'Optimized Storage Solution for Enterprise Scale Hyper-V Deployments'(PDF). Microsoft. March 2010. p. 15. Retrieved 25 October 2012.
External links[edit]
Look up snapshot in Wiktionary, the free dictionary. |
- Garimella, Neeta (2006-04-26). 'Understanding and exploiting snapshot technology for data protection, Part 1: Snapshot technology overview'.
- Harwood, Mike (2003-09-24). 'Storage Basics: Backup Strategies'.
HYCU spins out from Comtrade, continues to advance the HYCU purpose-built data protection for Nutanix Enterprise Cloud Platform. |
Anyone following enterprise data storage news couldn’t help but notice that aspects of the backup market are struggling badly. From its glory days of a couple of years back, the purpose-built backup appliance (PBBA), for example, has been trending downwards in terms of revenues per IDC.
'The PBBA market remains in a state of transition, posting a 16.2% decline in the second quarter of 2017,' said Liz Conner, an analyst at IDC. 'Following a similar trend to the enterprise storage systems market, the traditional backup market is declining as end users and vendors alike explore new technology.'
She’s talking about alternatives such as the cloud, replication and snapshots. But can these really replace backup?
Replication Grabs a Slice of the Pie
Backup Vs Snapshot
Cuong Le, Senior Vice President of Field Operations at Data Dynamics, does not believe backup is quite ready to join the dinosaurs. But he sees its functions being eaten away by snapshots and replication.
“For sure, backup is not dead, but its purpose is moving to an availability solution for near continuous data protection using snapshots and fast recovery of virtual machines,” he said. “Traditional file backup is being replaced by replication.
In support of that argument, he said new technology such as S3 compliant object storage provides built-in data protection using replication. The files are replicated to different sites and offer replacement of files that are lost or deleted by mistake. When the replication location is offsite, new object storage also protects from disasters.
However, he conceded that database applications that require high availability and high-speed flash storage will remain well served by backup solutions such as Veeam that focus on virtual machine protection and high availability.
Snapshot Backup Pc
Snapshots Good, Backup Better
Snapshots are clearly a good method of protecting data. Backup vendors such as Veritas have integrated snapshot technology, for example, into appliances for such tasks as capturing multiple versions of Oracle.

“We integrate with a variety of hardware snapshot technologies and most recently have introduced Veritas CloudPoint, designed to orchestrate cloud snapshots across multiple cloud environments,” said Dan O’Farrell, senior director of solutions marketing, Veritas. “However, having a snapshot is not enough. Organizations need a way to manage the retention of those snapshots, identify and catalog the contents of those snapshots, and a simple way to access the data within those snapshots without having to be a storage or snapshot expert.”
Integrated Data Protection
David King, Director of Solutions Marketing, Commvault, said modern data management is about keeping services running, and those services are all part of a stack: a compute platform that may be physical, virtual, or both; a database; an application; and a web server. It’s about backing up and restoring a service in total, and that requires complete knowledge of everything in that stack.
Beyond mere transmission of data onto tape or disk on a regular basis, then, backup now involves a whole lot of coordination with other areas of data storage. Snapshots and replication are a part of that, but they aren’t a replacement.
“Snapshots and replications should be integrated into your overall data protection, but not at the expense of the ability to move, manage, and use your data throughout your infrastructure that modern data protection solutions deliver,” said King.
RTO and RPO attainment
Christophe Bertrand, Vice President of Product Marketing at Arcserve, concurs. He said data protection is a continuum of technologies that only make sense when viewed against their ability to deliver Return Point Objectives (RPOs) and Return Time Objectives(RTOs). These RPOs and RTOs must meet business requirements.
“There is no question that we are now in a phase of maturity where end users should leverage unified data protection technology that approaches such as snapshots, deduplication, replication, nlock level incremental, and file copies,” said Bertrand. “In many ways, this is not your traditional backup anymore - it’s a new era in which, across all market segments but, in particular, in the mid-market, service levels are stringent.”
Different Focus

In any case, it’s perhaps a lazy look to lump snapshots, replication and backup into the same basket. Some might even say that one replaces the other. But that’s a narrow and misguided look.
“Snapshots and replication are not a replacement for backup,” said Linus Chang, CEO, BackupAssist.
Snapshots and replication supplement but are not a direct replacement for backup. They do a good job in some disaster recovery situations, but they have a different focus.
“Replication is about minimizing downtime and snapshots are about enabling the retrieval of old versions of data, whereas backup is all about redundancy,” said Chang. “All three things sound similar and they overlap each other, but one doesn’t fully replace another.”
Ransomware Protection
A recent spate of ransomware attacks has made it very clear that all data is at risk. Some strains have been targeting storage and snapshot files. Some, for instance, intentionally delete old VSS snapshots on a disk to make it impossible to go back to old versions. They’ll then start encrypting files, so if a replication system is used, those encrypted files will be copied across to the replica. You end up with a replica with corrupted files and no old versions (i.e. snapshots). What do you do now?
“Quite simply, it will be backups that save the day,” said Chang. “If you have a copy of your data sitting on a hard drive on your shelf, or stored on a cloud service, then you can get it back.”

Price
There are also practical considerations like price, added Chang. Backup is familiar and relatively inexpensive compared to snapshots and replication. On that basis alone, many small and mid-sized organizations with little or no IT staff are likely to cling to the familiar. Backup to tape or backup to the cloud and be done with it. It’s the simplest form of data protection and one that has been grooved in over many decades.
Snapshots Will Never Replace Backup
Just as backups can’t do everything that snapshots and replication offer, the same holds true in reverse. Frank Jablonksi, Vice President of Global Marketing at Acronis, believes snapshots are an essential part of any protection strategy. But they can never replace the need to store data copies locally for quick recovery and in a remote location in case of a local disaster.
“Snapshots are a great tool for making a copy quickly and returning a machine to production as fast as possible,” he said. “However, they often are not catalogued to facilitate finding data for recovery and are stored locally so they don’t help if your data center has an outage.”
Point in Time
The main issue with replication is that it does not create point in time copies of data. Therefore, software corruption or malware can easily destroy a replicated copy of data. Instead, you need a backup that is a true point in time copy of your data and stored in a remote location such as a cloud or another datacenter, separated by a good distance from your originating data center.
Data Backup And Data Snapshot Difference
“Ransomware has become a huge problem and your recourse without paying the ransom is to completely recover your systems from your backup,” said Jablonski. “Today’s backup applications need strong security to protect against ransomware attacks. They need to be stored off-line in another location, and the backup application hardened to prevent injection attacks and other nefarious behavior that would destroy the backed-up data.”
Teamwork
Online Data Backup
Obviously, it’s not a matter of backups or snapshots or replication. Jablonski see them as part of the same data recovery team.
Data Backup Process
“Backup applications make good use of snapshots by allowing the snapshot to make the initial copy of the data that the backup application then processes as a true point in time backup for recovery,” he said.