SNIA SDC 2018 recap

[Vijay Singh]

I was there as well Alan :)

On Mon, Oct 22, 2018, 9:13 AM Alan Somers <asomers at freebsd.org> wrote:

> The SNIA Storage Developers' Conference was held in Santa Clara during the
> last week of September.  Jim Harris, John Hixon, Nick Principe, Michael
> Dexter, and myself attended.  As far as FreeBSD goes, here's a summary of
> the juiciest bits:
>
> NVDIMM/PMEM: A lot of companies are still pushing persistent memory
> products.  They're getting better, but still quite vendor-specific.
> Fortunately, there are standardization efforts in place.  JEDEC is
> standardizing the hardware (NVDIMM-N, NVDIMM-P, NVDIMM-F).  Every major
> memory company (but not CPU company) is on-board.  SNIA is also trying to
> standardize a programming model (but not the precise API).  Windows and
> Linux currently support it, with differences.  There will probably be some
> additional changes to the model.
> https://static.ptbl.co/static/attachments/187585/1537988510.pdf?1537988510
> .  iX Systems reported some impressive benchmarks using an NVDIMM as a ZFS
> slog device.  Several databases are adding pmem support.  A few filesystems
> have some level of NVDIMM support, and the NOVA filesystem is being written
> from the ground up to take full advantage of NVDIMM.  For example,
> directories are stored as in-memory data structures that never get
> serialized.  The lesson here is that FreeBSD needs to support the standard
> NVDIMM programming model too.
>
> OpenChannel SSDs: These are SSDs that expose more of their internal
> implementation details to the host.  Specifically, they rely on the host
> for at least part of garbage collection.  They also expose their multiple
> internal busses to the host, so it can choose how to stripe data across
> them.  Overall, the programming model is surprisingly similar to that of
> SMR hard drives.  Unfortunately, the standard is a bit murky.  Different
> speakers could not even agree on whether there is a standard.  This is the
> best presentation on the topic:
> https://static.ptbl.co/static/attachments/187321/1537829929.pdf?1537829929
> and this is the closest thing there is to a standard ATM:
> https://openchannelssd.readthedocs.io/en/latest/ .  The lesson here is
> that
> FreeBSD needs to plumb these devices' properties up to userland and perhaps
> expose them in zonectl(8) (easy) and add filesystem support (very hard).
>
> NVMe: If there were an award for most popular buzzword, it would've gone to
> "NVMe".  Everybody and their mother had something to say about it.  But I
> personally paid little attention (except as regards OpenChannel).
>
> Seagate dual-actuator hard drives: Seagate is coming out with hard drives
> that pack two servos into a single case.  Each servo can access half of the
> platters.  The drive reports each servo as a separate LUN to the host.
> There is little FreeBSD needs to do here.  To make zfsd(8) work correctly,
> we should add lun info to the drives' physical path strings.  And it might
> be nice if zpool(8) prevented the user from adding both LUNs of the same
> physical drive to the same RAID group.  But that's arguably out of our
> domain.
>
> SPDK: The storage-plane developer's kit is like Intel's version of Netmap,
> but for storage.  It's a say for userland programs to access storage
> devices directly, bypassing the kernel.  The benefits are negligible for
> spinning media, but can be significant for fast NVMe drives.  SPDK has
> multiple backends for different I/O controllers, including some that are
> kernel-based.  Notably lacking is a POSIX AIO backend.  That's probably the
> biggest gap in its FreeBSD support.
>
> iX Systems wrote a blog post about the conference, too.  It covers
> Swordfish and Samba, two topics I ignored.
>
> https://www.ixsystems.com/blog/snia-sdc-2018/
>
> -Alan
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