Filter
Top Products
312 Administering volume snapshots
Cascaded snapshots
to recover the mirror volume in the same way as for a
DISABLED volume. See “Starting a volume” on page 271.
If you resize (that is, grow or shrink) a volume, all its ACTIVE linked mirror
volumes are also resized at the same time. The volume and its mirrors can be in
the same disk group or in different disk groups. If the operation is successful,
the volume and its mirrors will have the same size.
If a volume has been grown, a resynchronization of the grown regions in its
linked mirror volumes is started, and the links remain in the ATTACHING state
until resynchronization is complete. The
vxsnap snapwait command can be
used to wait for the state to become ACTIVE.
When you use the vxsnap make command to create the snapshot volume, this
removes the link, and establishes a snapshot relationship between the snapshot
volume and the original volume.
The
vxsnap reattach operation re-establishes the link relationship between the
two volumes, and starts a resynchronization of the mirror volume.
See “Creating and managing linked break-off snapshot volumes” on page 331
for details of the procedures for creating and using this type of snapshot.
For information about how to prepare an empty volume for use by full-sized
instant snapshots, see “Creating a volume for use as a full-sized instant or
linked break-off snapshot” on page 323.
Cascaded snapshots
A snapshot hierarchy known as a snapshot cascade can improve write
performance for some applications. Instead of having several independent
snapshots of the volume, it is more efficient to make the older snapshots into
children of the latest snapshot as shown in Figure 9-4.
Figure 9-4 Snapshot cascade
A snapshot may be added to a cascade by specifying the
infrontof attribute to
the
vxsnap make command when the second and subsequent snapshots in the
cascade are created. Changes to blocks in the original volume are only written to
the most recently created snapshot volume in the cascade. If an attempt is made
Oldest
snapshot
Most recent
snapshot
Original
volume
V
Snapshot
volume
Sn
Snapshot
volume
Sn-1
Snapshot
volume
S1
. . .