VERITAS FlashSnap Point-In-Time-Copy Solutions Administrator's Guide
VERITAS Software Used in Point-In-Time Copy Scenarios
6 VERITAS FlashSnap Point-In-Time Copy Solutions Administrator’s Guide
◆ VERITAS Storage Foundation Installation Guide
◆ VERITAS File System Administrator’s Guide
◆ VERITAS NetBackup DataCenter Installation Guide
◆ VERITAS NetBackup DataCenter System Administrator’s Guide
◆ VERITAS NetBackup ServerFree Agent System Administrator’s Guide
◆ VERITAS NetBackup for Oracle ServerFree Agent System Administrator’s Guide
◆ VERITAS NetBackup BusinesServer Getting Started Guide
◆ VERITAS NetBackup BusinesServer System Administrator’s Guide
◆ VERITAS Volume Manager Administrator’s Guide
Persistent FastResync of Volume Snapshots
VERITAS Volume Manager allows you to take multiple snapshots of your data at the level of a
volume. A snapshot volume contains a stable copy of a volume’s data at a given moment in time
that you can use for online backup or decision support. If Persistent FastResync is enabled on a
volume, VxVM uses a FastResync map to keep track of which blocks are updated in the volume
and in the snapshot. If the data in one mirror is not updated for some reason, it becomes out-of-date,
or stale, with respect to the other mirrors in the volume. The presence of the FastResync map
means that only those updates that the mirror has missed need be reapplied to resynchronize it with
the volume. A full, and thereby much slower, resynchronization of the mirror from the volume is
unnecessary.
When snapshot volumes are reattached to their original volumes, Persistent FastResync allows the
snapshot data to be quickly refreshed and re-used. Persistent FastResync uses disk storage to ensure
that FastResync maps survive both system and cluster crashes. If Persistent FastResync is enabled
on a volume in a private disk group, incremental resynchronization can take place even if the host
is rebooted.
Persistent FastResync can track the association between volumes and their snapshot volumes after
they are moved into different disk groups. After the disk groups are rejoined, Persistent FastResync
allows the snapshot plexes to be quickly resynchronized.
For more information, see the VERITAS Volume Manager Administrator’s Guide.
Instant Volume Snapshots
The traditional type of volume snapshot that was provided in VxVM is of the third-mirror type.
This name comes from its original implementation by adding an additional plex to a mirrored
volume. After the contents of the third-mirror (or snapshot plex) had been synchronized from the
original plexes of the volume, it could be detached as a snapshot volume for use in backup or