We are going to deprecate drive-backup, so don't mention it here. Moreover, blockdev-backup seems more correct in the context. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; --- docs/block-replication.txt | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/docs/block-replication.txt b/docs/block-replication.txt index 108e9166a8..59eb2b33b3 100644 --- a/docs/block-replication.txt +++ b/docs/block-replication.txt @@ -79,7 +79,7 @@ Primary | || Secondary disk <--------- hidden-disk 5 <--------- || | | || | | || '-------------------------' - || drive-backup sync=none 6 + || blockdev-backup sync=none 6 1) The disk on the primary is represented by a block device with two children, providing replication between a primary disk and the host that @@ -101,7 +101,7 @@ should support bdrv_make_empty() and backing file. that is modified by the primary VM. It should also start as an empty disk, and the driver supports bdrv_make_empty() and backing file. -6) The drive-backup job (sync=none) is run to allow hidden-disk to buffer +6) The blockdev-backup job (sync=none) is run to allow hidden-disk to buffer any state that would otherwise be lost by the speculative write-through of the NBD server into the secondary disk. So before block replication, the primary disk and secondary disk should contain the same data. -- 2.29.2

We are going to deprecate drive-backup, so use modern interface here. In examples where target image creation is shown, show blockdev-add as well. If target creation omitted, omit blockdev-add as well. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov(a)virtuozzo.com&gt; --- docs/interop/bitmaps.rst | 285 +++++++++++++++++++++++++++++---------- 1 file changed, 215 insertions(+), 70 deletions(-) diff --git a/docs/interop/bitmaps.rst b/docs/interop/bitmaps.rst index 059ad67929..ef95090c81 100644 --- a/docs/interop/bitmaps.rst +++ b/docs/interop/bitmaps.rst @@ -539,12 +539,11 @@ other partial disk images on top of a base image to reconstruct a full backup from the point in time at which the incremental backup was issued. The "Push Model" here references the fact that QEMU is "pushing" the modified -blocks out to a destination. We will be using the `drive-backup -<qemu-qmp-ref.html#index-drive_002dbackup>`_ and `blockdev-backup -<qemu-qmp-ref.html#index-blockdev_002dbackup>`_ QMP commands to create both +blocks out to a destination. We will be using the `blockdev-backup +<qemu-qmp-ref.html#index-blockdev_002dbackup>`_ QMP command to create both full and incremental backups. -Both of these commands are jobs, which have their own QMP API for querying and +The command is a job, which has its own QMP API for querying and management documented in `Background jobs <qemu-qmp-ref.html#Background-jobs>`_. @@ -557,6 +556,10 @@ create a new incremental backup chain attached to a drive. This example creates a new, full backup of "drive0" and accompanies it with a new, empty bitmap that records writes from this point in time forward. +The target may be created with help of `blockdev-add +<qemu-qmp-ref.html#index-blockdev_002dadd>`_ or `blockdev-create +<qemu-qmp-ref.html#index-blockdev_002dcreate>`_ command. + .. note:: Any new writes that happen after this command is issued, even while the backup job runs, will be written locally and not to the backup destination. These writes will be recorded in the bitmap @@ -576,12 +579,11 @@ new, empty bitmap that records writes from this point in time forward. } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive0", - "target": "/path/to/drive0.full.qcow2", - "sync": "full", - "format": "qcow2" + "target": "target0", + "sync": "full" } } ] @@ -664,12 +666,11 @@ use a transaction to reset the bitmap while making a new full backup: } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive0", - "target": "/path/to/drive0.new_full.qcow2", - "sync": "full", - "format": "qcow2" + "target": "target0", + "sync": "full" } } ] @@ -728,19 +729,35 @@ Example: First Incremental Backup $ qemu-img create -f qcow2 drive0.inc0.qcow2 \ -b drive0.full.qcow2 -F qcow2 +#. Add target block node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc0.qcow2" + } + } + } + + <- { "return": {} } + #. Issue an incremental backup command: .. code-block:: QMP -> { - "execute": "drive-backup", + "execute": "blockdev-backup", "arguments": { "device": "drive0", "bitmap": "bitmap0", - "target": "drive0.inc0.qcow2", - "format": "qcow2", - "sync": "incremental", - "mode": "existing" + "target": "target0", + "sync": "incremental" } } @@ -785,20 +802,36 @@ Example: Second Incremental Backup $ qemu-img create -f qcow2 drive0.inc1.qcow2 \ -b drive0.inc0.qcow2 -F qcow2 +#. Add target block node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc1.qcow2" + } + } + } + + <- { "return": {} } + #. Issue a new incremental backup command. The only difference here is that we have changed the target image below. .. code-block:: QMP -> { - "execute": "drive-backup", + "execute": "blockdev-backup", "arguments": { "device": "drive0", "bitmap": "bitmap0", - "target": "drive0.inc1.qcow2", - "format": "qcow2", - "sync": "incremental", - "mode": "existing" + "target": "target0", + "sync": "incremental" } } @@ -866,20 +899,36 @@ image: file for you, but you lose control over format options like compatibility and preallocation presets. +#. Add target block node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc2.qcow2" + } + } + } + + <- { "return": {} } + #. Issue a new incremental backup command. Apart from the new destination image, there is no difference from the last two examples. .. code-block:: QMP -> { - "execute": "drive-backup", + "execute": "blockdev-backup", "arguments": { "device": "drive0", "bitmap": "bitmap0", - "target": "drive0.inc2.qcow2", - "format": "qcow2", - "sync": "incremental", - "mode": "existing" + "target": "target0", + "sync": "incremental" } } @@ -930,6 +979,38 @@ point in time. $ qemu-img create -f qcow2 drive0.full.qcow2 64G $ qemu-img create -f qcow2 drive1.full.qcow2 64G +#. Add target block nodes: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.full.qcow2" + } + } + } + + <- { "return": {} } + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target1", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive1.full.qcow2" + } + } + } + + <- { "return": {} } + #. Create a full (anchor) backup for each drive, with accompanying bitmaps: .. code-block:: QMP @@ -953,21 +1034,19 @@ point in time. } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive0", - "target": "/path/to/drive0.full.qcow2", - "sync": "full", - "format": "qcow2" + "target": "target0", + "sync": "full" } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive1", - "target": "/path/to/drive1.full.qcow2", - "sync": "full", - "format": "qcow2" + "target": "target1", + "sync": "full" } } ] @@ -1016,6 +1095,38 @@ point in time. $ qemu-img create -f qcow2 drive1.inc0.qcow2 \ -b drive1.full.qcow2 -F qcow2 +#. Add target block nodes: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc0.qcow2" + } + } + } + + <- { "return": {} } + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target1", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive1.inc0.qcow2" + } + } + } + + <- { "return": {} } + #. Issue a multi-drive incremental push backup transaction: .. code-block:: QMP @@ -1025,25 +1136,21 @@ point in time. "arguments": { "actions": [ { - "type": "drive-backup", + "type": "blockev-backup", "data": { "device": "drive0", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive0.inc0.qcow2" + "target": "target0" } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive1", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive1.inc0.qcow2" + "target": "target1" } }, ] @@ -1119,19 +1226,35 @@ described above. This example demonstrates the single-job failure case: $ qemu-img create -f qcow2 drive0.inc0.qcow2 \ -b drive0.full.qcow2 -F qcow2 +#. Add target block node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc0.qcow2" + } + } + } + + <- { "return": {} } + #. Attempt to create an incremental backup via QMP: .. code-block:: QMP -> { - "execute": "drive-backup", + "execute": "blockdev-backup", "arguments": { "device": "drive0", "bitmap": "bitmap0", - "target": "drive0.inc0.qcow2", - "format": "qcow2", - "sync": "incremental", - "mode": "existing" + "target": "target0", + "sync": "incremental" } } @@ -1164,6 +1287,19 @@ described above. This example demonstrates the single-job failure case: "event": "BLOCK_JOB_COMPLETED" } +#. Remove target node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-del", + "arguments": { + "node-name": "target0", + } + } + + <- { "return": {} } + #. Delete the failed image, and re-create it. .. code:: bash @@ -1172,20 +1308,36 @@ described above. This example demonstrates the single-job failure case: $ qemu-img create -f qcow2 drive0.inc0.qcow2 \ -b drive0.full.qcow2 -F qcow2 +#. Add target block node: + + .. code-block:: QMP + + -> { + "execute": "blockdev-add", + "arguments": { + "node-name": "target0", + "driver": "qcow2", + "file": { + "driver": "file", + "filename": "drive0.inc0.qcow2" + } + } + } + + <- { "return": {} } + #. Retry the command after fixing the underlying problem, such as freeing up space on the backup volume: .. code-block:: QMP -> { - "execute": "drive-backup", + "execute": "blockdev-backup", "arguments": { "device": "drive0", "bitmap": "bitmap0", - "target": "drive0.inc0.qcow2", - "format": "qcow2", - "sync": "incremental", - "mode": "existing" + "target": "target0", + "sync": "incremental" } } @@ -1210,7 +1362,8 @@ described above. This example demonstrates the single-job failure case: Example: Partial Transactional Failures ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -QMP commands like `drive-backup <qemu-qmp-ref.html#index-drive_002dbackup>`_ +QMP commands like `blockdev-backup +<qemu-qmp-ref.html#index-blockdev_002dbackup>`_ conceptually only start a job, and so transactions containing these commands may succeed even if the job it created later fails. This might have surprising interactions with notions of how a "transaction" ought to behave. @@ -1240,25 +1393,21 @@ and one succeeds: "arguments": { "actions": [ { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive0", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive0.inc0.qcow2" + "target": "target0" } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive1", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive1.inc0.qcow2" + "target": "target1" } }] } @@ -1375,25 +1524,21 @@ applied: }, "actions": [ { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive0", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive0.inc0.qcow2" + "target": "target0" } }, { - "type": "drive-backup", + "type": "blockdev-backup", "data": { "device": "drive1", "bitmap": "bitmap0", - "format": "qcow2", - "mode": "existing", "sync": "incremental", - "target": "drive1.inc0.qcow2" + "target": "target1" } }] } -- 2.29.2

On Wed, May 05, 2021 at 04:58:03PM +0300, Vladimir Sementsov-Ogievskiy wrote: The core changes itself looks good; I have some minor nit-picks below, hope that's not annoying. :-) With those addressed: Reviewed-by: Kashyap Chamarthy <kchamart(a)redhat.com&gt; nit: s/deprecated ``drive-backup``/the deprecated ``drive-backup``/ Here too, missing the article "the": "the deprecated". nit: Let's consistently spell QEMU in all caps, please: s/Qemu/QEMU/ s/from/from the/ I might slightly rephrase it this way: ``blockdev-backup`` differs from ``drive-backup`` in how you specify the backup target. Can use literals also for node-name: s/node-name/``node-name`` s/to/to an/ s/``blockdev-backup``/``blockdev-backup`` command/ nit: s/in pair/in combination/ The rest reads good to me. Thanks for fixing this. [...] -- /kashyap