QSnap is a snapshot technology developed solely by Qsan. Snapshot is a very cost-efficient application to protect your valuable data. It's a popluar technique used in backup solution, disaster recovery and data protection.
A snapshot primarily creates a point-in-time copy of the data. Before snapshots can be taken, you need to set aside storage space dedicated to keep snapshot data. QSnap uses "copy-on-write" technique to implement snapshot function. When the snapshot is first created, only the meta-data about where original data is stored is copied. No physical copy of the data is done at the time the snapshot is created. So taking a snapshot is almost instantaneous. Nothing gets stored until a request of data modification comes in. The snapshot copies the original data to snapshot space and then overwrites the original data with new changes. With this technique, snapshot only copies the changed data instead of copying whole data. It is highly space efficient. Besides, the snapshot requires the original copy of the data to be valid.
Here are some takeaway points of Qsan snapshot technology.
Controller-based (hardware driven, block device) snapshot instead of host-based (file system) snapshot. No CPU resource is taken on hosts/servers.