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4.4 Snapshot (QSnap) / Rollback
Snapshot-on-the-box (QSnap) 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 its
previous state at a time the snapshot was captured. 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. Refer to Figure 4.4.1 for snapshot concept.
Figure 4.4.1
Caution
Snapshot / rollback features need 512MB RAM at least. Please
also refer to RAM certification l ist in Appendix A.
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