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•
Perform backups of the file system from a snapshot instead of using the
live file system
Snapshots are rule-based, with the flexibility to define when they are taken
based on business policies. Rules-based snapshots provide entity
management, a more useful configuration compared to simpler volume-
based snapshot management. For example, hourly snapshot rules are
managed as one entity, daily or weekly rules are managed as a separate
entity, and monthly rules are managed as a 3rd separate entity. There is
also an implied hierarchy to snapshot rules: an hourly snapshot will not
overwrite a daily or weekly snapshot, etc. An hourly snapshot will overwrite
only another hourly snapshot, a daily or weekly snapshot will only overwrite
a snapshot taken because of a daily or weekly rule, etc.
Snapshots can be set up in four ways:
•
Automatically, via a prescribed rule
•
Manually, using the servers' GUI or CLI management interfaces
•
Scripted, using a script, the storage administrator may automate the
beginning of the snapshot process, in a manner similar to the rules-
based method described above
•
Event based, using scripts and the remote scripting tool, the storage
administrator may automate the taking of a snapshot based on trigger
events generated by the server
Space efficient clones
File clones provide the ability to instantly create space-efficient, writeable
copies of single files. This is a key feature for virtualization, as it allows
VMware administrators to quickly deploy new virtual machines without
consuming additional disk space.
When a file clone is created, a hidden file-level and read-only snapshot is
created which preserves an image of the source file at that point in time.
This snapshot allows the source file and clone to share common data blocks.
If additional clones of the source file are created, new snapshots are created
if necessary.
The key benefits of file clones include:
•
Space efficiency: File clones are initially created through the use of
pointers to blocks. No data is duplicated, and only new file writes are
saved to the file system.
•
Speed: File clones are created in seconds, regardless of the size of the
file being cloned.
•
Flexibility: File clones are created per file, allowing for a VMware virtual
machine focused view of file cloning.
Specific features of file clones include writable snapshots, clone of a clone
(or cascading clones), deep copy, and unlimited number of file clones.
3–8
Software overview
Hitachi Unified Storage VM Product Overview Guide
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