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

[ adding Jan and Ross ] On Wed, Jan 31, 2018 at 5:03 PM, Dan Williams <dan.j.williams(a)intel.com&gt; wrote: > On Wed, Jan 31, 2018 at 4:45 PM, Andiry Xu <andiry(a)gmail.com&gt; 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