User manual

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5.4
iSnap
Snapshot-on-the-box (iSnap) captures the instant state of data in the target volume
in a logical sense. The underlying logic is Copy-on-Write -- moving out the data which
would be written to certain location where a write action occurs since the time of data
capture. The certain location, named as “Snap VD”, is essentially a new VD which
can be attached to a LUN provisioned to a host as a disk like other ordinary VDs in
the system. Rollback restores the data back to the state of any time which was
previously captured in case for any unfortunate reason it might be (e.g. virus attack,
data corruption, human errors and so on). Snap VD is allocated within the same RG
in which the snapshot is taken, we suggest to reserve 20% of RG size or more for
snapshot space. Please refer to the following figure for snapshot concept.
Figure 5.4.1
Tips
The size of VD extension must be larger than original.
Caution
VD Extension cannot be executed during rebuilding or migration.
RAG362