Re: [Qemu-devel] [PATCH 0/8] add basic recovery logic to quorum driver

["Benoît Canet" <benoit.canet@irqsave.net>]

The Monday 01 Sep 2014 à 15:43:06 (+0800), Liu Yuan wrote :
> This patch set mainly add mainly two logics to implement device recover
> - notify qourum driver of the broken states from the child driver(s)
> - dirty track and sync the device after it is repaired
> 
> Thus quorum allow VMs to continue while some child devices are broken and when
> the child devices are repaired and return back, we sync dirty bits during
> downtime to keep data consistency.
> 
> The recovery logic is based on the driver state bitmap and will sync the dirty
> bits with a timeslice window in a coroutine in this prtimive implementation.
> 
> Simple graph about 2 children with threshold=1 and read-pattern=fifo:
> (similary to DRBD)
> 
> + denote device sync iteration
> - IO on a single device
> = IO on two devices
> 
>                                       sync complete, release dirty bitmap
>                                          ^
>                                          |
>   ====-----------------++++----++++----++==========
>      |                 |
>      |                 v
>      |               device repaired and begin to sync
>      v
>    device broken, create a dirty bitmap
> 
>   This sync logic can take care of nested broken problem, that devices are
>   broken while in sync. We just start a sync process after the devices are
>   repaired again and switch the devices from broken to sound only when the sync
>   completes.
> 
> For read-pattern=quorum mode, it enjoys the recovery logic without any problem.

Hi Liu,

I had something like that in mind.

This series seems very cool I will review it.

Thanks for contributing to quorum.

Best regards

Benoît

> 
> Todo:
> - use aio interface to sync data (multiple transfer in one go)
> - dynamic slice window to control sync bandwidth more smoothly
> - add auto-reconnection mechanism to other protocol (if not support yet)
> - add tests
> 
> Cc: Eric Blake <eblake@redhat.com>
> Cc: Benoit Canet <benoit@irqsave.net>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Stefan Hajnoczi <stefanha@redhat.com>
> 
> Liu Yuan (8):
>   block/quorum: initialize qcrs.aiocb for read
>   block: add driver operation callbacks
>   block/sheepdog: propagate disconnect/reconnect events to upper driver
>   block/quorum: add quorum_aio_release() helper
>   quorum: fix quorum_aio_cancel()
>   block/quorum: add broken state to BlockDriverState
>   block: add two helpers
>   quorum: add basic device recovery logic
> 
>  block.c                   |  17 +++
>  block/quorum.c            | 324 +++++++++++++++++++++++++++++++++++++++++-----
>  block/sheepdog.c          |   9 ++
>  include/block/block.h     |   9 ++
>  include/block/block_int.h |   6 +
>  trace-events              |   5 +
>  6 files changed, 336 insertions(+), 34 deletions(-)
> 
> -- 
> 1.9.1
>