Re: [Qemu-devel] [Patch v12 resend 00/10] Block replication for continuous checkpoints
* Wen Congyang (we...@cn.fujitsu.com) wrote:
> On 12/23/2015 06:04 PM, Stefan Hajnoczi wrote:
> > On Thu, Dec 17, 2015 at 02:22:14PM +0800, Wen Congyang wrote:
> >> Stefan:Ping...
> >>
> >> What about this feature? I have worked for it about 1 year, but it is
> >> still in the
> >> way...
> >
> > The code still has TODOs. What is the plan for supporting replication
> > after failover? This feature seems critical because anyone who wants FT
> > won't be able to use this code unless it supports FT after the first
> > failure.
>
> We have implemented it based on an old version qemu. To keep the logical
> simple, we don't post them now. We will post them after this feature is merged
> into qemu.
It's probably best to post them, or at least say how you intend to do it,
so people can get an understanding of which way you're going.
However, why is anything new needed to continue replication after failover?
Shouldn't it be possible to build the secondary's disk structure in a way
that it can (by device/disk add/remove) into a structure that looks the same
as a primary, and then we just start a new migration to the new secondary?
(There's a separate problem of getting that to work with the rest of COLO as
well)
Dave
>
> >
> > ---
> >
> > Adding new block layer APIs that are replication-specific is not clean.
> > Only the replication block driver cares about the start/stop/checkpoint
> > interface.
> >
> > It is cleaner to have a separate API and data structure for block
> > replication.
> >
> > The replication code should define its own BlockReplicationOps struct
> > and allow objects to register themselves. Then it's no longer necessary
> > to modify the core block layer to forward start/stop/checkpoint calls.
> >
> > Something like:
> >
> > typedef struct BlockReplicationOps BlockReplicationOps;
> > typedef struct BlockReplicationState {
> > const BlockReplicationOps *ops;
> > QLIST_ENTRY(BlockReplicationState) list;
> > } BlockReplicationState;
> >
> > typedef struct {
> > void start(BlockReplicationState *brs, Error **errp);
> > void stop(BlockReplicationState *brs, Error **errp);
> > void checkpoint(BlockReplicationState *brs, Error **errp);
> > } BlockReplicationOps;
> >
> > static QLIST_HEAD(BlockReplicationState) block_replication_states;
> >
> > void block_replication_add(BlockReplicationState *brs);
> > void block_replication_remove(BlockReplicationState *brs);
> >
> > The replication block driver would add/remove itself. The quorum block
> > driver probably doesn't need to be modified (I think in your current
> > patches you modify it just to forward the start/stop/checkpoint calls to
> > a particular quorum child).
>
> Yes, it is the major purpose. We also do some check in the quorum driver:
> we don't allow more than one child support block replication.
>
> Thanks
> Wen Congyang
>
> >
> > Stefan
> >
>
>
>
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
Re: [Qemu-devel] [Patch v12 resend 00/10] Block replication for continuous checkpoints
On Thu, Dec 17, 2015 at 02:22:14PM +0800, Wen Congyang wrote:
> Stefan:Ping...
>
> What about this feature? I have worked for it about 1 year, but it is still
> in the
> way...
The code still has TODOs. What is the plan for supporting replication
after failover? This feature seems critical because anyone who wants FT
won't be able to use this code unless it supports FT after the first
failure.
---
Adding new block layer APIs that are replication-specific is not clean.
Only the replication block driver cares about the start/stop/checkpoint
interface.
It is cleaner to have a separate API and data structure for block
replication.
The replication code should define its own BlockReplicationOps struct
and allow objects to register themselves. Then it's no longer necessary
to modify the core block layer to forward start/stop/checkpoint calls.
Something like:
typedef struct BlockReplicationOps BlockReplicationOps;
typedef struct BlockReplicationState {
const BlockReplicationOps *ops;
QLIST_ENTRY(BlockReplicationState) list;
} BlockReplicationState;
typedef struct {
void start(BlockReplicationState *brs, Error **errp);
void stop(BlockReplicationState *brs, Error **errp);
void checkpoint(BlockReplicationState *brs, Error **errp);
} BlockReplicationOps;
static QLIST_HEAD(BlockReplicationState) block_replication_states;
void block_replication_add(BlockReplicationState *brs);
void block_replication_remove(BlockReplicationState *brs);
The replication block driver would add/remove itself. The quorum block
driver probably doesn't need to be modified (I think in your current
patches you modify it just to forward the start/stop/checkpoint calls to
a particular quorum child).
Stefan
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Re: [Qemu-devel] [Patch v12 resend 00/10] Block replication for continuous checkpoints
On 12/23/2015 06:04 PM, Stefan Hajnoczi wrote:
> On Thu, Dec 17, 2015 at 02:22:14PM +0800, Wen Congyang wrote:
>> Stefan:Ping...
>>
>> What about this feature? I have worked for it about 1 year, but it is still
>> in the
>> way...
>
> The code still has TODOs. What is the plan for supporting replication
> after failover? This feature seems critical because anyone who wants FT
> won't be able to use this code unless it supports FT after the first
> failure.
We have implemented it based on an old version qemu. To keep the logical
simple, we don't post them now. We will post them after this feature is merged
into qemu.
>
> ---
>
> Adding new block layer APIs that are replication-specific is not clean.
> Only the replication block driver cares about the start/stop/checkpoint
> interface.
>
> It is cleaner to have a separate API and data structure for block
> replication.
>
> The replication code should define its own BlockReplicationOps struct
> and allow objects to register themselves. Then it's no longer necessary
> to modify the core block layer to forward start/stop/checkpoint calls.
>
> Something like:
>
> typedef struct BlockReplicationOps BlockReplicationOps;
> typedef struct BlockReplicationState {
> const BlockReplicationOps *ops;
> QLIST_ENTRY(BlockReplicationState) list;
> } BlockReplicationState;
>
> typedef struct {
> void start(BlockReplicationState *brs, Error **errp);
> void stop(BlockReplicationState *brs, Error **errp);
> void checkpoint(BlockReplicationState *brs, Error **errp);
> } BlockReplicationOps;
>
> static QLIST_HEAD(BlockReplicationState) block_replication_states;
>
> void block_replication_add(BlockReplicationState *brs);
> void block_replication_remove(BlockReplicationState *brs);
>
> The replication block driver would add/remove itself. The quorum block
> driver probably doesn't need to be modified (I think in your current
> patches you modify it just to forward the start/stop/checkpoint calls to
> a particular quorum child).
Yes, it is the major purpose. We also do some check in the quorum driver:
we don't allow more than one child support block replication.
Thanks
Wen Congyang
>
> Stefan
>
Re: [Qemu-devel] [Patch v12 resend 00/10] Block replication for continuous checkpoints
Stefan:Ping... What about this feature? I have worked for it about 1 year, but it is still in the way... On 12/02/2015 01:31 PM, Wen Congyang wrote: > Block replication is a very important feature which is used for > continuous checkpoints(for example: COLO). > > You can get the detailed information about block replication from here: > http://wiki.qemu.org/Features/BlockReplication > > Usage: > Please refer to docs/block-replication.txt > > This patch series is based on the following patch series: > 1. http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg04949.html > 2. http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg06043.html > > You can get the patch here: > https://github.com/coloft/qemu/tree/wency/block-replication-v12 > > You can get the patch with framework here: > https://github.com/coloft/qemu/tree/wency/colo_framework_v11.2 > > TODO: > 1. Continuous block replication. It will be started after basic functions >are accepted. > > Changs Log: > V12: > 1. Rebase to the newest codes > 2. Use backing reference to replcace 'allow-write-backing-file' > V11: > 1. Reopen the backing file when starting blcok replication if it is not >opened in R/W mode > 2. Unblock BLOCK_OP_TYPE_BACKUP_SOURCE and BLOCK_OP_TYPE_BACKUP_TARGET >when opening backing file > 3. Block the top BDS so there is only one block job for the top BDS and >its backing chain. > V10: > 1. Use blockdev-remove-medium and blockdev-insert-medium to replace backing >reference. > 2. Address the comments from Eric Blake > V9: > 1. Update the error messages > 2. Rebase to the newest qemu > 3. Split child add/delete support. These patches are sent in another patchset. > V8: > 1. Address Alberto Garcia's comments > V7: > 1. Implement adding/removing quorum child. Remove the option non-connect. > 2. Simplify the backing refrence option according to Stefan Hajnoczi's > suggestion > V6: > 1. Rebase to the newest qemu. > V5: > 1. Address the comments from Gong Lei > 2. Speed the failover up. The secondary vm can take over very quickly even >if there are too many I/O requests. > V4: > 1. Introduce a new driver replication to avoid touch nbd and qcow2. > V3: > 1: use error_setg() instead of error_set() > 2. Add a new block job API > 3. Active disk, hidden disk and nbd target uses the same AioContext > 4. Add a testcase to test new hbitmap API > V2: > 1. Redesign the secondary qemu(use image-fleecing) > 2. Use Error objects to return error message > 3. Address the comments from Max Reitz and Eric Blake > > Wen Congyang (10): > unblock backup operations in backing file > Store parent BDS in BdrvChild > Backup: clear all bitmap when doing block checkpoint > Allow creating backup jobs when opening BDS > docs: block replication's description > Add new block driver interfaces to control block replication > quorum: implement block driver interfaces for block replication > Implement new driver for block replication > support replication driver in blockdev-add > Add a new API to start/stop replication, do checkpoint to all BDSes > > block.c| 145 > block/Makefile.objs| 3 +- > block/backup.c | 14 ++ > block/quorum.c | 78 +++ > block/replication.c| 549 > + > blockjob.c | 11 + > docs/block-replication.txt | 227 +++ > include/block/block.h | 9 + > include/block/block_int.h | 15 ++ > include/block/blockjob.h | 12 + > qapi/block-core.json | 34 ++- > 11 files changed, 1093 insertions(+), 4 deletions(-) > create mode 100644 block/replication.c > create mode 100644 docs/block-replication.txt >
[Qemu-devel] [Patch v12 resend 00/10] Block replication for continuous checkpoints
Block replication is a very important feature which is used for continuous checkpoints(for example: COLO). You can get the detailed information about block replication from here: http://wiki.qemu.org/Features/BlockReplication Usage: Please refer to docs/block-replication.txt This patch series is based on the following patch series: 1. http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg04949.html 2. http://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg06043.html You can get the patch here: https://github.com/coloft/qemu/tree/wency/block-replication-v12 You can get the patch with framework here: https://github.com/coloft/qemu/tree/wency/colo_framework_v11.2 TODO: 1. Continuous block replication. It will be started after basic functions are accepted. Changs Log: V12: 1. Rebase to the newest codes 2. Use backing reference to replcace 'allow-write-backing-file' V11: 1. Reopen the backing file when starting blcok replication if it is not opened in R/W mode 2. Unblock BLOCK_OP_TYPE_BACKUP_SOURCE and BLOCK_OP_TYPE_BACKUP_TARGET when opening backing file 3. Block the top BDS so there is only one block job for the top BDS and its backing chain. V10: 1. Use blockdev-remove-medium and blockdev-insert-medium to replace backing reference. 2. Address the comments from Eric Blake V9: 1. Update the error messages 2. Rebase to the newest qemu 3. Split child add/delete support. These patches are sent in another patchset. V8: 1. Address Alberto Garcia's comments V7: 1. Implement adding/removing quorum child. Remove the option non-connect. 2. Simplify the backing refrence option according to Stefan Hajnoczi's suggestion V6: 1. Rebase to the newest qemu. V5: 1. Address the comments from Gong Lei 2. Speed the failover up. The secondary vm can take over very quickly even if there are too many I/O requests. V4: 1. Introduce a new driver replication to avoid touch nbd and qcow2. V3: 1: use error_setg() instead of error_set() 2. Add a new block job API 3. Active disk, hidden disk and nbd target uses the same AioContext 4. Add a testcase to test new hbitmap API V2: 1. Redesign the secondary qemu(use image-fleecing) 2. Use Error objects to return error message 3. Address the comments from Max Reitz and Eric Blake Wen Congyang (10): unblock backup operations in backing file Store parent BDS in BdrvChild Backup: clear all bitmap when doing block checkpoint Allow creating backup jobs when opening BDS docs: block replication's description Add new block driver interfaces to control block replication quorum: implement block driver interfaces for block replication Implement new driver for block replication support replication driver in blockdev-add Add a new API to start/stop replication, do checkpoint to all BDSes block.c| 145 block/Makefile.objs| 3 +- block/backup.c | 14 ++ block/quorum.c | 78 +++ block/replication.c| 549 + blockjob.c | 11 + docs/block-replication.txt | 227 +++ include/block/block.h | 9 + include/block/block_int.h | 15 ++ include/block/blockjob.h | 12 + qapi/block-core.json | 34 ++- 11 files changed, 1093 insertions(+), 4 deletions(-) create mode 100644 block/replication.c create mode 100644 docs/block-replication.txt -- 2.5.0
