Yes.

That's another consensus of the block-level log-structured caching
works that I've introduced in the previous post.

For example, NetApp's Mercury (2012) has the following sentence 
indicating that
it also copy data to in-memory buffer and write it (called log chunk in
the paper but I call dm-writeboost's equivalent "RAM buffer") to cache 
device
when it gets full.
```
Once a successful acknowledgment is received, an I/O command’s data is
copied to an in-memory buffer, called a log chunk, and the command is
completed to the upper layer. The log chunk is written to the cache 
device when full.
```

- Akira

On 2015/02/21 0:06, Joe Thornber wrote:
> On Fri, Feb 20, 2015 at 05:44:01PM +0900, Akira Hayakawa wrote:
>> I will wait for ack from dm maintainers.
> Are you still copying the contents of every bio to your own memory
> buffer before writing it to disk?
>
> - Joe