Re: [dm-devel] [PATCH RFC v1 01/01] dm-lightnvm: An open FTL for open firmware SSDs

[Matias Bjorling]

On 03/24/2014 07:22 PM, Akira Hayakawa wrote:
> Hi, Matias,
> 
> Sorry for jumping in. I am interested in this new feature, too.
> 
>>> Does it even make sense to expose the underlying devices as block
>>> devices?  It surely would help to send this together with a driver
>>> that you plan to use it on top of.
>>>
>>
>> Agree, an underlying driver is missing. My first plan is to get a draft
>> firmware for the OpenSSD to be stable and expose its primitives
>> (read/write/erase) up through the ATA/SCSI stack. Communicating using
>> vendor specific codes.
> 

Hi Akira,

Indeed. Most of Mohit's work can be applied with this layer. In the same
breath we could also look into nameless writes. It would up open for a
new design for co-operating file systems.

> Exposing FTL to the host layer has potential to share mapping in cache software (or driver) and the device.
> The "Unified Address Space" in the slides below addresses the problem of two levels of indirection.
> http://www1.unine.ch/eurosys2012/posters/saxena.pdf
> 
> Developing API to share mapping between driver and the device sounds interesting, too.
> 
> --
> Akira
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