SANRAD V-Switch St Write to Source and Update to 1st Snapshot, Advanced Volume Operations 145

B
	QA Testing			Snapshot1
S	A	N	S
N	A	S	H
A	M	M	O
P	U	N	T
	QA Testing			Snapshot1
B	A	N	S	S
N	A	S	H
A	M	M	O	10264
P	U	N	T

Figure 76. 1st Write to Source and Update to 1st 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.

Asnapshot can have read-write or read-only access and, when exposed, it must be exposed on the same V-Switch as its source volume.

Chapter 8: Advanced Volume Operations 145