EMC CX500I Configuration Guide - Page 69

Clone and Snapshot Trade-offs, Snapshots of Clones

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Data Replication and Data Mobility Software Clone and Snapshot Trade-offs The following table describes the benefits and trade-offs of using clones, snapshots, and snapshots of clones. Table 4-2 A Comparison of Clones and Snapshots Clones Snapshots Snapshots of Clones Benefits • Provides enhanced protection against critical data loss because it is an actual LUN. • Provides immediacy in replacing the contents of the source LUN with the contents of the clone LUN, should the source become corrupted. • Provides immediacy in redirecting hosts from the source LUN to the clone LUN, should the source become corrupted. • Makes backup operation of a clone nondisruptive. Provides a quick and instant copy because it is a virtual LUN (provided that the snapshot is used in conjunction with a backup operation). Provides an extra level of protection against critical data loss if both the source LUN and clone LUN become corrupted. Creation Time Minutes to hours. The creation time depends on the size of Instantaneous the source LUN. Instantaneous Disk Space Used Uses the same amount of disk space as the source LUN. Uses reserved LUN pool space, which is usually 10% to 20% of the source LUN size, but will vary depending on how much data has changed on the source LUN. Uses reserved LUN pool space (for the snapshot) and full disk space (for the clone), which usually totals 110% to 120% of the source LUN size, but will vary depending on how much data has changed on the source LUN. Data Recovery Time After Source LUN Failure/ Corruption Instantaneous after initializing a reverse synchronization. Restore time from network or backup tape. Restore time from network or backup tape if fractured clone received host I/O. Performance • There is no performance impact when a clone is in a A slight performance Impact on the fractured state. Storage System • For the initial synchronization of the clone, decrease due to the copy-on-first-write. performance decreases. Subsequent synchronizations have minimal impact on performance. • For synchronizations and reverse synchronizations, the performance decrease is the same as an initial synchronization but for a shorter period of time. Impact is also determined by the synchronization rate, which is set when the clone is added to the Clone Group. Combination of both clones and snapshots. What Is SnapView? 4-7

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What Is SnapView?
4-7
Data Replication and Data Mobility Software
Clone and Snapshot Trade-offs
The following table describes the benefits and trade-offs of using
clones, snapshots, and snapshots of clones.
Table 4-2
A Comparison of Clones and Snapshots
Clones
Snapshots
Snapshots of Clones
Benefits
•
Provides enhanced protection against critical data loss
because it is an actual LUN.
•
Provides immediacy in replacing the contents of the
source LUN with the contents of the clone LUN, should
the source become corrupted.
•
Provides immediacy in redirecting hosts from the
source LUN to the clone LUN, should the source
become corrupted.
•
Makes backup operation of a clone nondisruptive.
Provides a quick and
instant copy because
it is a virtual LUN
(provided that the
snapshot is used in
conjunction with a
backup operation).
Provides an extra level of
protection against critical
data loss if both the
source LUN and clone
LUN become corrupted.
Creation Time
Minutes to hours. The creation time depends on the size of
the source LUN.
Instantaneous
Instantaneous
Disk Space
Used
Uses the same amount of disk space as the source LUN.
Uses reserved LUN
pool space, which is
usually 10% to 20%
of the source LUN
size, but will vary
depending on how
much data has
changed on the
source LUN.
Uses reserved LUN pool
space (for the snapshot)
and full disk space (for
the clone), which usually
totals 110% to 120% of
the source LUN size, but
will vary depending on
how much data has
changed on the source
LUN.
Data Recovery
Time After
Source LUN
Failure/
Corruption
Instantaneous after initializing a reverse synchronization.
Restore time from
network or backup
tape.
Restore time from
network or backup tape if
fractured clone received
host I/O.
Performance
Impact on the
Storage System
•
There is no performance impact when a clone is in a
fractured state.
•
For the initial synchronization of the clone,
performance decreases. Subsequent synchronizations
have minimal impact on performance.
•
For synchronizations and reverse synchronizations, the
performance decrease is the same as an initial
synchronization but for a shorter period of time. Impact
is also determined by the synchronization rate, which is
set when the clone is added to the Clone Group.
A slight performance
decrease due to the
copy-on-first-write.
Combination of both
clones and snapshots.