SNIA SDC 2018 recap
Alan Somers
asomers at freebsd.org
Mon Oct 22 16:34:01 UTC 2018
Ahh, I didn't notice. Were you associated with your employer?
-Alan
On Mon, Oct 22, 2018 at 10:23 AM Vijay Singh <vijju.singh at gmail.com> wrote:
> 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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