HP Storage Mirroring V5.1 Software - Manual (Page 96)

14 - 2
Understanding when to take a snapshot
A snapshot may not necessarily be useful if the data on the target is in a bad state. You only want
snapshots of data that is in a good state. Therefore, you need to understand when the data is in a
good or bad state.
Action State Description
Automatic Action
Taken for Scheduled
and Automatic
Snapshots
User Interaction
Required for Manual
Snapshots
Mirror
Started
Bad Mirroring has started,
but is not complete.
The data on the source
and target will not be
synchronized until the
mirror is complete.
Scheduled and
automatic snapshots
will be delayed until the
mirror is complete
before taking a
snapshot.
Wait until the mirror is
complete and the data
is in a good state, then
take a manual
snapshot.
Mirror
Stopped
Bad Mirroring has stopped
without completing.
The data on the source
and target will not be
synchronized until the
mirror is complete.
Scheduled and
automatic snapshots
will be delayed until the
mirror has been
restarted and is
complete before taking
a snapshot.
Restart the mirror, wait
until it is complete and
the data is in a good
state, and then take a
manual snapshot.
Mirror
Complete
Good Because the mirror is
complete, the data on
the source and target is
synchronized. Storage
Mirroring will take a
snapshot while the data
is in a good state.
Scheduled and
automatic snapshots
will occur normally.
Manual snapshots can
be taken normally.
Write
Operation
Retried
Good An operation cannot be
written to the hard
drive on the target. For
example, the file could
be in use by another
application on the
target.
Scheduled and
automatic snapshots
will occur normally,
although the operation
that is being retried will
not be included in the
snapshot.
Manual snapshots can
be taken normally,
although the operation
that is being retried will
not be included in the
snapshot.
Write
Operation
Dropped
Bad An operation could not
be written to the hard
drive on the target,
even after multiple
retries. For example,
the file could be in use
by another application
on the target.
An automatic snapshot
will be taken just prior
to the operation being
dropped.
Scheduled snapshots
will be delayed until the
target data is back in a
good state.
Start a mirror, wait
until it is complete and
the data is in a good
state, and then take a
manual snapshot.
Write
Operation
Succeeded
Good An operation that was
retrying on the target
has been successfully
written to the hard
drive.
Scheduled and
automatic snapshots
will occur normally.
Manual snapshots can
be taken normally.
Target
Restarted
with
Connection
Persistance
Good The target service was
able to persist
connection information
prior to restarting.
Scheduled and
automatic snapshots
will occur normally.
Manual snapshots can
be taken normally.