Dynamic granularity in data replication

A method comprising:

• sending a snapshot of a primary volume to a replica site, sending the snapshot of the primary volume comprises sending a first snapshot of the primary volume to form a third snapshot;
• determining if a bandwidth is available to send changes in the primary volume to the replica site to allow any point in time recovery of data in the primary volume;
• sending the changes from the primary volume if the bandwidth is available;
• tracking the changes in a local journal:
• generating a second snapshot of the primary volume;
• sending the differences between the first and second snapshots to the replica site:
• generating a fourth snapshot at the replica site by applying the differences between the first and second snapshots to the third snapshot;
• and
• if the bandwidth is not available:
• erasing the local journal;
• renaming the second snapshot to be the first snapshot;
• and
• repeating the tracking of changes in the local journal.

An apparatus, comprising:

• electronic hardware circuitry configured to:
• send a snapshot of a primary volume to a replica site;
• determine if a bandwidth is available to send changes in the primary volume to the replica site to allow any point in time recovery of data in the primary volume;
• send the changes from the primary volume if the bandwidth is available;
• track the changes in a local journal;
• generate a second snapshot of the primary volume:
• send the differences between a first snapshot and the second snapshot to the replica site;
• generate a fourth snapshot at the replica site by applying the differences between the first and second snapshots to a third snapshot;
• and
• access an intermediary snapshot between the first snapshot and the second snapshot comprising circuitry,
• wherein the circuitry configured to send a snapshot of the primary volume comprises circuitry configured to send the first snapshot of the primary volume to form the third snapshot,
• wherein the circuitry configured to access an intermediary snapshot between the first snapshot and the second snapshot comprises circuitry configured to:
• copy the third snapshot to form an intermediary snapshot;
• for each journal entry in a difference journal, determine if the journal entry includes I/O data;
• apply I/O data from the difference journal to the intermediary snapshot if the journal entry comprises I/O data;
• and
• apply I/O data pointed to by the difference journal if the journal entry does not include I/O data.

An apparatus, comprising:

• electronic hardware circuitry configured to:
• send a snapshot of a primary volume to a replica site;
• determine if a bandwidth is available to send changes in the primary volume to the replica site to allow any point in time recovery of data in the primary volume;
• send the changes from the primary volume if the bandwidth is available;
• track the changes in a local journal;
• generate a second snapshot of the primary volume:
• send the differences between a first snapshot and the second snapshot to the replica site;
• generate a fourth snapshot at the replica site by applying the differences between the first and second snapshots to a third snapshot;
• erase the local journal if the bandwidth is not available;
• rename the second snapshot to be the first snapshot if the bandwidth is not available;
• and
• repeat the tracking of changes in the local journal if bandwidth is not available,
• wherein the circuitry configured to send a snapshot of the primary volume comprises circuitry configured to send the first snapshot of the primary volume to form the third snapshot.

An article comprising:

• a non-transitory computer-readable medium that stores computer-executable instructions, the instructions causing a machine to:
• send a snapshot of a primary volume to a replica site;
• determine if a bandwidth is available to send changes in the primary volume to the replica site to allow any point in time recovery of data in the primary volume;
• send the changes from the primary volume if the bandwidth is available;
• track the changes in a local journal;
• generate a second snapshot of the primary volume:
• send the differences between a first snapshot and the second snapshot to the replica site;
• generate a fourth snapshot at the replica site by applying the differences between the first and second snapshots to a third snapshot;
• and
• access an intermediary snapshot between the first snapshot and the second snapshot,
• wherein the instructions causing the machine to send a snapshot of the primary volume comprises instructions causing the machine to send a first snapshot of the primary volume to form a third snapshot,
• wherein the instructions causing the machine to access an intermediary snapshot between the first snapshot and the second snapshot comprises instructions causing the machine to:
• copy the third snapshot to form an intermediary snapshot;
• for each journal entry in a difference journal, determine if the journal entry includes I/O data;
• apply I/O data from the difference journal to the intermediary snapshot if the journal entry comprises I/O data;
• and
• apply I/O data pointed to by the difference journal if the journal entry does not include I/O data.

An article comprising:

• a non-transitory computer-readable medium that stores computer-executable instructions, the instructions causing a machine to:
• send a snapshot of a primary volume to a replica site;
• determine if a bandwidth is available to send changes in the primary volume to the replica site to allow any point in time recovery of data in the primary volume;
• send the changes from the primary volume if the bandwidth is available;
• track the changes in a local journal;
• generate a second snapshot of the primary volume;
• send the differences between a first snapshot and the second snapshot to the replica site;
• generate a fourth snapshot at the replica site by applying the differences between the first and second snapshots to a third snapshot;
• erase the local journal if the bandwidth is not available;
• rename the second snapshot to be the first snapshot if the bandwidth is not available;
• and
• repeat the tracking of changes in the local journal if bandwidth is not available,
• wherein the instructions causing the machine to send a snapshot of the primary volume comprises instructions causing the machine to send a first snapshot of the primary volume to form a third snapshot.