Re: [LSF/MM TOPIC] Native NVMM file systems

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, Jan 31, 2018 at 04:45:36PM -0800, Andiry Xu wrote:
> PMEM/DAX should allow for significant improvements in file system
> performance and enable new programming models that allow direct,
> efficient access to PMEM from userspace.  Achieving these gains in
> existing file systems built for block devices (e.g., XFS and EXT4…)
> presents a range of challenges (e.g.,
> https://lkml.org/lkml/2016/9/11/159) and has been the subject of a lot
> of recent work on ext4 and xfs.
> 
> An alternative is to build a NVMM-aware file system from scratch that
> takes full advantage of the performance that PMEM offers and avoids
> the complexity that block-based file systems include to maximize
> performance on slow storage (e.g., relaxing atomicity constraints on
> many operations).  Of course, it also brings with it the complexity of
> another file system.
>
> We recently sent out a patch set for one-such “clean slate” NVMM-aware
> file system called NOVA.  NOVA is log-structured DAX file system with
> several nice features:

That's the series that was sent out last August, correct?

> * High performance, especially in metadata operations due to efficient
> fine-grained logging
> * High scalability with per-CPU memory pool and per-inode logging
> * Strong metadata and data atomicity guarantees for all operations
> * Full filesystem snapshot support with DAX-mmap
> * Metadata replication/checksums and RAID-4 style data protection
> 
> At the summit, we would like to discuss the trade-offs between
> adapting NVMM features to existing file systems vs. creating/adopting
> a purpose-built file system for NVMM.  NOVA serves as useful starting
> point for that discussion by demonstrating what’s possible.  It may
> also suggest some features that could be adapted to other file systems
> to improve NVMM performance.
> 
> We welcome people that are interested in file systems and NVM/DAX.
> Particular people that would be useful to have in attendance are Dan
> Williams, Dave Chinner, and Matthew Wilcox.

I wouldn't mind being there too. :)

--D

> 
> Thanks,
> Andiry

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