February OpenZFS Leadership Meeting

[Matthew Ahrens]

Thanks to everyone who participated at this month's meeting.  We discussed:

   - Thread priorities on linux
   - Feature flag activation bug
   - Moving of the OpenZFS website to University of Washington
   - FOSDEM, Scale, and other conferences


The recording is now available: https://www.youtube.com/watch?v=upUOXBhx-us

Thanks Serapheim for taking notes:

   -

   Thread priorities on linux (Paul D)
   -

      Context: Performance analysis of ZFS send on ZFSonLinux found
      discrepancies with illumos
      -

      Root cause: Linux the threads are minimum priority, lower than user
      threads (as opposed to Illumos)
      -

      Workaround: Increased the priority for now
      -

      Question: How do we want to deal with this among different OS’s?
      -

         FreeBSD has the same priority scheme as illumos (Linux being the
         outlier of the 3)
         -

         In Linux there were performance issues related with thread
         priorities in the past but there hasn’t been any recent investigations
         -

         There is no silver bullet for this
         -

      Consensus:
      -

         There are not many thread cases whose performance we don’t care
         about but we should at least break down threads into
different groups and
         decide on the priority of each group
         -

         This issue is to be added to the list of issues that we need an
         open PR on GIthub for discussion
         -

   Do we need to enhance the feature flag activation code. Setting
   checksum=sha512 or compress=zstd but not writing any blocks, can cause the
   pool to panic on older systems
   -

      Summary: Setting the compression to zstd but you don’t write any
      blocks, and then re-import that pool in a ZFS version that doesn’t
      understand zstd triggers an assertion failure
      -

      Consensus:
      -

         Bump the counter when the feature gets activated AND for each
         block created with it (refcount never goes to zero until the
dataset is
         destroyed).
         -

         Although seemingly difficult to implement we should at least pay a
         close look at the code paths as it may not be as intractable
as it seems.
         -

   Support for ignoring (not being able to mount) datasets with unsupported
   feature flags
   -

      Consensus: This is a good idea in general but it should not be
      considered a solution for the aforementioned zstd problem.
      -

   Moving of the OpenZFS website from Joyent to University of Washington is
   in-progress
   -

      No problems with Joyent, just planning for the long-term
      -

      No actual website changes, just the DNS endpoint will change
      -

      Still would be happy to update any contributions to update the
      website’s content :)
      -

   Changes that need reviewers:
   -

      Persistent L2ARC - https://github.com/zfsonlinux/zfs/pull/9582
      -

      Performance Optimization for Encryption
      -

         Includes new algorithms and changing the default algorithm used
         -

         Action Item: Send an email to the mailing list as a heads up about
         changing the default before going ahead an applying that change
         -

   FOSDEM, Scale, and other conferences
   -

      There doesn’t seem to be any talks related to ZFS in the
      aforementioned conferences but people attending can submit BoF discussions
      -

         iXsystems will potentially be at Scale this year
         -

      Allan Jude has done a ZFS-related talk in the main track of FOSDEM in
      the past
      -

      There will be a ZFS BoF in this year’s BSDCan and potentially one
      ZFS-related talk too.
      -

      The BSDNow podcast is open to interview people doing interesting work
      on ZFS
      -

      General Idea: It would be good to be active in conferences and groups
      outside of the OpenZFS summit and BSD
      -

         On this note, OpenZFS is considering spinning up funds for people
         that want to work on that (e.g. setting up a booth on those
conferences and
         getting the word out).


On Mon, Feb 3, 2020 at 1:26 PM Matthew Ahrens <mahrens at delphix.com> wrote:

> The next OpenZFS Leadership meeting will be held tomorrow, February 4,
> 1pm-2pm Pacific time.  The agenda is pretty light this month, so if you
> have any topics you'd like to discuss with the group, tomorrow will be a
> good opportunity :-)
>
> Everyone is welcome to attend and participate, and we will try to keep the
> meeting on agenda and on time.  The meetings will be held online via Zoom,
> and recorded and posted to the website and YouTube after the meeting.
>
> The agenda for the meeting will be a discussion of the projects listed in
> the agenda doc.
>
> For more information and details on how to attend, as well as notes and
> video from the previous meeting, please see the agenda document:
>
>
> https://docs.google.com/document/d/1w2jv2XVYFmBVvG1EGf-9A5HBVsjAYoLIFZAnWHhV-BM/edit
>
> --matt
>