iSCSI GbE to SAS/SATA II RAID Subsystem
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User Manual
4.4 Snapshot / Rollback
Snapshot-on-the-box
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 figure below for the snapshot concept.
IMPORTANT! Snapshot / rollback features need at least 1 GB
controller cache RAM. Please also refer to RAM certification list in
Appendix A.
