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docs/interop/bitmaps: use blockdev-backup 

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.

Reviewed-by: Kashyap Chamarthy <kchamart@redhat.com>
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2021-11-04 09:58:10 +01:00
parent 9a599217a4
commit 24d6cc1fa1
1 changed files with 215 additions and 70 deletions
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285
docs/interop/bitmaps.rst
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@ -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 background 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 can be created with the 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"
}
}]
}