11:45 a.m.
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.
Thanks,
Andiry