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

[Dan Williams <dan.j.williams@intel.com>]

[ adding Jan and Ross ]

On Wed, Jan 31, 2018 at 5:03 PM, Dan Williams <dan.j.williams@intel.com> wrote:
> On Wed, Jan 31, 2018 at 4:45 PM, Andiry Xu <andiry@gmail.com> 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:
>>
>> * 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.
>
> The rest of the fs-dax crew would also be useful to have:
>
> Jan Kara
> Ross Zwisler

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