Provisioning Snapshots; Snapshots Versus Backups; Write Patterns And Parity In Network Raid-6 (Dual Parity) - HP StorageWorks P4000 User Manual

1. P1 is parity for data blocks A, B, C, D
2. P2 is parity for data blocks E, F, G, H
3. P3 is parity for data blocks I, J, K, L
4. P4 is parity for data blocks M, N, O, P
Figure 73 Write patterns and parity in Network RAID-6 (Dual Parity)
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Provisioning snapshots

Snapshots provide a copy of a volume for use with backup and other applications. You create
snapshots from a volume on the cluster.
Snapshots are always thin provisioned. Thin provisioning snapshots saves actual space in the SAN,
while letting you have more snapshots without the concern of running out of cluster space.
Snapshots can be used for multiple purposes, including:
• Source volumes for data mining and other data use
• Source volumes for creating backups
• Data or file system preservation before upgrading software
• Protection against data deletion
• File-level restore without tape or backup software

Snapshots versus backups

Backups are typically stored on different physical devices such as tapes. Snapshots are stored in the
same cluster as the volume. Therefore, snapshots protect against data deletion, but not device or
storage media failure. Use snapshots along with backups to improve your overall data backup strategy.
196 Provisioning storage