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Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replica
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module) |
Date: |
Wed, 8 Feb 2012 14:59:40 +0000 |
On Wed, Feb 8, 2012 at 2:59 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Wed, Feb 8, 2012 at 1:28 PM, Ori Mamluk <address@hidden> wrote:
>> Hi,
>> Thanks for all the valuable inputs provided so far, I'll try to suggest a
>> design based on them.
>> The main inputs were about the use a new transport protocol between repagent
>> and rephub.
>> It was suggested to use some standard network storage protocol instead, and
>> use QMP commands for the control path.
>>
>> The main idea is to use two NBD connections per protected volume:
>> NBD tap - protected VM is the client, rephub is the server, used to report
>> writes.
>> The tap is not a standard NBD backing - it is for replication, meaning
>> that its importance is lesser than
>> the main image path. Errors are not reported to the protected VM as IO
>> error.
>
> You mentioned a future feature that sends request metadata (offset,
> length) to the rephub synchronously so that protection is 100%.
> (Otherwise a network failure or crash might result in missed writes
> that the rephub does not know about.)
>
> The NBD tap might not be the right channel for sending synchronous
> request metadata, since the protocol is geared towards block I/O
> requests that include the actual data. I'm not sure that QMP should
> be used either - even though we have the concept of QMP events -
> because it's not a low-latency, high ops communications channel.
>
> Which channel do you use in your existing products for synchronous
> request metadata?
BTW, your design makes sense to me.
Stefan
- Re: [Qemu-devel] [RFC PATCH] replication agent module, (continued)
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Ori Mamluk, 2012/02/07
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Paolo Bonzini, 2012/02/07
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Ori Mamluk, 2012/02/08
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Dor Laor, 2012/02/08
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Stefan Hajnoczi, 2012/02/08
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Kevin Wolf, 2012/02/08
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Ori Mamluk, 2012/02/08
- Re: [Qemu-devel] [RFC PATCH] replication agent module, Kevin Wolf, 2012/02/08
- Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module), Ori Mamluk, 2012/02/08
- Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module), Stefan Hajnoczi, 2012/02/08
- Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module),
Stefan Hajnoczi <=
- Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module), Ori Mamluk, 2012/02/19
- Re: [Qemu-devel] [RFC] Replication agent design (was [RFC PATCH] replication agent module), Paolo Bonzini, 2012/02/20
- [Qemu-devel] BlockDriverState stack and BlockListeners (was: [RFC] Replication agent design), Kevin Wolf, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Paolo Bonzini, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Kevin Wolf, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Paolo Bonzini, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Kevin Wolf, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Paolo Bonzini, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Stefan Hajnoczi, 2012/02/21
- Re: [Qemu-devel] BlockDriverState stack and BlockListeners, Paolo Bonzini, 2012/02/21