224:. 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.
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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
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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.
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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.
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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
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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.
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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
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file systems support creating snapshots (cloning) of individual files. Additionally, Btrfs also supports the creation of snapshots of subvolumes. On AIX,
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269:(LVM) allows creation of both read-only and read-write snapshots. Writable snapshots were introduced with the LVM version 2 (LVM2).
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provides snapshots via the same VSS interface for shared storage. Snapshots have also been available in the NSS (
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469:"Optimized Storage Solution for Enterprise Scale Hyper-V Deployments"
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of a large data set may take a long time to complete. On
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203:systems, however, cannot bear service stoppages.
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257:Some volume managers also allow creation of
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109:Learn how and when to remove this message
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47:adding citations to reliable sources
514:"Storage Basics: Backup Strategies"
474:. Microsoft. March 2010. p. 15
374:Apple File System § Snapshots
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58:"Snapshot" computer storage
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536:Fault-tolerant computer systems
497:Garimella, Neeta (2006-04-26).
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476:. Retrieved
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41:Please help
36:verification
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541:Persistence
444:"LVM HOWTO"
319:Shadow Copy
147:photography
525:Categories
478:25 October
454:2013-09-29
450:. tldp.org
430:References
311:Windows XP
265:On Linux,
249:on entire
69:newspapers
345:product.
295:namespace
212:read-only
153:Rationale
368:See also
327:Melio FS
259:writable
208:snapshot
197:downtime
186:approach
139:snapshot
335:NetWare
190:locking
157:A full
141:is the
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531:Backup
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283:fossil
171:atomic
159:backup
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410:Notes
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354:Btrfs
339:Linux
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237:Some
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127:Btrfs
90:JSTOR
76:books
480:2012
362:JFS2
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299:UFS2
285:for
279:WAFL
239:Unix
221:O(1)
201:24/7
184:One
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