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[Qemu-devel] [PULL 16/29] docs: Document how to stream to an intermediat
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 16/29] docs: Document how to stream to an intermediate layer |
Date: |
Mon, 31 Oct 2016 18:25:45 +0100 |
From: Alberto Garcia <address@hidden>
Signed-off-by: Alberto Garcia <address@hidden>
Reviewed-by: Kevin Wolf <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
docs/live-block-ops.txt | 36 +++++++++++++++++++++++++-----------
1 file changed, 25 insertions(+), 11 deletions(-)
diff --git a/docs/live-block-ops.txt b/docs/live-block-ops.txt
index a257087..2211d14 100644
--- a/docs/live-block-ops.txt
+++ b/docs/live-block-ops.txt
@@ -4,15 +4,20 @@ LIVE BLOCK OPERATIONS
High level description of live block operations. Note these are not
supported for use with the raw format at the moment.
+Note also that this document is incomplete and it currently only
+covers the 'stream' operation. Other operations supported by QEMU such
+as 'commit', 'mirror' and 'backup' are not described here yet. Please
+refer to the qapi/block-core.json file for an overview of those.
+
Snapshot live merge
===================
Given a snapshot chain, described in this document in the following
format:
-[A] -> [B] -> [C] -> [D]
+[A] <- [B] <- [C] <- [D] <- [E]
-Where the rightmost object ([D] in the example) described is the current
+Where the rightmost object ([E] in the example) described is the current
image which the guest OS has write access to. To the left of it is its base
image, and so on accordingly until the leftmost image, which has no
base.
@@ -21,11 +26,14 @@ The snapshot live merge operation transforms such a chain
into a
smaller one with fewer elements, such as this transformation relative
to the first example:
-[A] -> [D]
+[A] <- [E]
+
+Data is copied in the right direction with destination being the
+rightmost image, but any other intermediate image can be specified
+instead. In this example data is copied from [C] into [D], so [D] can
+be backed by [B]:
-Currently only forward merge with target being the active image is
-supported, that is, data copy is performed in the right direction with
-destination being the rightmost image.
+[A] <- [B] <- [D] <- [E]
The operation is implemented in QEMU through image streaming facilities.
@@ -35,14 +43,20 @@ streaming operation completes it raises a QMP event.
'block_stream'
copies data from the backing file(s) into the active image. When finished,
it adjusts the backing file pointer.
-The 'base' parameter specifies an image which data need not be streamed from.
-This image will be used as the backing file for the active image when the
-operation is finished.
+The 'base' parameter specifies an image which data need not be
+streamed from. This image will be used as the backing file for the
+destination image when the operation is finished.
+
+In the first example above, the command would be:
+
+(qemu) block_stream virtio0 file-A.img
-In the example above, the command would be:
+In order to specify a destination image different from the active
+(rightmost) one we can use its node name instead.
-(qemu) block_stream virtio0 A
+In the second example above, the command would be:
+(qemu) block_stream node-D file-B.img
Live block copy
===============
--
1.8.3.1
- [Qemu-devel] [PULL 07/29] block: Pause all jobs during bdrv_reopen_multiple(), (continued)
- [Qemu-devel] [PULL 07/29] block: Pause all jobs during bdrv_reopen_multiple(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 08/29] block: Add block_job_add_bdrv(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 09/29] block: Use block_job_add_bdrv() in mirror_start_job(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 10/29] block: Use block_job_add_bdrv() in backup_start(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 03/29] block/ssh: Add InetSocketAddress and accept it, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 11/29] block: Check blockers in all nodes involved in a block-commit job, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 14/29] block: Support streaming to an intermediate layer, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 13/29] block: Block all intermediate nodes in commit_active_start(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 15/29] block: Add QMP support for streaming to an intermediate layer, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 12/29] block: Block all nodes involved in the block-commit operation, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 16/29] docs: Document how to stream to an intermediate layer,
Kevin Wolf <=
- [Qemu-devel] [PULL 17/29] qemu-iotests: Test streaming to an intermediate layer, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 18/29] qemu-iotests: Test block-stream operations in parallel, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 22/29] qemu-iotests: Test streaming to a Quorum child, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 20/29] qemu-iotests: Test block-stream and block-commit in parallel, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 21/29] qemu-iotests: Add iotests.supports_quorum(), Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 19/29] qemu-iotests: Test overlapping stream and commit operations, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 24/29] qemu-iotests: Test the 'base-node' parameter of 'block-stream', Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 23/29] block: Add 'base-node' parameter to the 'block-stream' command, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 27/29] block: Mention replication in BlockdevDriver enum docs, Kevin Wolf, 2016/10/31
- [Qemu-devel] [PULL 29/29] qapi: allow blockdev-add for NFS, Kevin Wolf, 2016/10/31