User manual

Chapter 8: Advanced Volume Operations 145
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Figure 76. 1
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Write to Source and Update to 1
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Snapshot
The more active the write operations are to a source volume, the more
capacity its snapshots need to have. SANRAD requires a beginning
snapshot volume of at least one percent of the size of its source volume. A
snapshot volume can be resized to accommodate a growing capacity need.
A snapshot volume has a user-defined load threshold to monitor when a
snapshot approaches full capacity. When the load threshold is exceeded, an
alert is sent to resize the volume. See “Resizing a Volume,” page 153.
A snapshot volume contains a table of pointers detailing which volume to
read from, the source or the snapshot, for each sector. For this reason, the
full capacity of a snapshot volume is not available for source copying. The
table size is:
(Size of Source Volume in blocks)/[(256)(Size of a Block in Snapshot/4)]
Deleting a snapshot volume has no effect on other snapshot volumes of the
same source.
A snapshot can have read-write or read-only access and, when exposed, it
must be exposed on the same V-Switch as its source volume.