Hi Congyang,
On Thu, 02/12 11:07, Wen Congyang wrote:
> +== Workflow ==
> +The following is the image of block replication workflow:
> +
> + +----------------------+ +------------------------+
> + |Primary Write Requests| |Secondary Write Requests|
> + +----------------------+ +------------------------+
> + | |
> + | (4)
> + | V
> + | /-------------\
> + | Copy and Forward | |
> + |---------(1)----------+ | Disk Buffer |
> + | | | |
> + | (3) \-------------/
> + | speculative ^
> + | write through (2)
> + | | |
> + V V |
> + +--------------+ +----------------+
> + | Primary Disk | | Secondary Disk |
> + +--------------+ +----------------+
> +
> + 1) Primary write requests will be copied and forwarded to Secondary
> + QEMU.
> + 2) Before Primary write requests are written to Secondary disk, the
> + original sector content will be read from Secondary disk and
> + buffered in the Disk buffer, but it will not overwrite the existing
> + sector content in the Disk buffer.
I'm a little confused by the tenses ("will be" versus "are") and terms. I am
reading them as "s/will be/are/g"
Why do you need this buffer?
If both primary and secondary write to the same sector, what is saved in the
buffer?
Fam
> + 3) Primary write requests will be written to Secondary disk.
> + 4) Secondary write requests will be buffered in the Disk buffer and it
> + will overwrite the existing sector content in the buffer.
> +
