Re: Adding compression/checksum support for bluestore.

[Igor Fedotov <ifedotov@mirantis.com>]

On 31.03.2016 21:38, Allen Samuels wrote:
>> Another thing to consider is an ability to use introduced checksums for
>> scrubbing. One can probably extend objectstore interface to be able to
>> validate stored data without data sending back.
>> I don't see such an option at the moment. Please correct me if I missed that.
> No need for that option. Just read the data check the return code (good or checksum failure) then discard the data. This is essentially exactly the same code-path as a "please validate the checksum" specialized opcode.
>
I'd rather disagree.
In fact one can perform object verification more effectively when using 
specific op:

- No need for decompression that's present in the read data-path
- No need to select proper read  buffer size. Verify operation can run 
over blob map instead of lextent one and read data by pextents.
- Verify can be done via single op call.
- IMHO code is more elegant and readable having specific op handler. In 
your option one has to Implement  "sub data-path" for read handler to 
discard data and do other optimizations if any... More flags, if 
statements, etc...