add v3 blog post

Author: alimanfoo

_posts/2019-06-19-zarr-v3-update.md

@@ -0,0 +1,71 @@
+---
+layout: post
+title:  "Zarr protocol v3 design update"
+date:   2019-06-19
+categories: zarr specs
+---
+
+Today I put together some [slides summarising the current state of
+exploratory work on the Zarr v3 protocol
+spec](https://zarr-developers.github.io/slides/v3-update-20190619.html). The
+purpose of this blog post is to share those slides more widely, and to
+provide some context explaining why work has started on a v3 spec.
+
+## Why work on a v3 spec?
+
+The [current (v2) Zarr
+spec](https://zarr.readthedocs.io/en/stable/spec/v2.html) is
+implemented in a number of software libraries, and is a stable and
+robust protocol that is used in production in a number of different
+scientific communities. If you need to store and compute in parallel
+against large array-like data, it's a good solution. So why start
+thinking about a new protocol version?
+
+### Language-agnostic
+
+One reason is that the v2 protocol is somewhat Python-centric, and
+includes some features which are not straightforward to implement in
+other languages. This has meant that implementations do not all
+support the same feature set. It would be good to have a minimal v3
+protocol spec that could be fully implemented in any language, so all
+implementations have parity around a core feature set.
+
+### Unifying Zarr and N5
+
+Another reason is that we would like to merge development efforts
+between the Zarr and N5 communities, and so a goal for the v3 spec is
+to unify the two approaches and provide a common implementation
+target.
+
+### Extensibility
+
+A third reason is that a number of different groups have started
+experimenting and extending the Zarr protocol in interesting ways, but
+it's not always clear how to extend the v2 protocol to support new
+features. It would be good if the v3 spec provided a variety of clear
+extension points and extension mechanisms.
+
+### Cloud storage
+
+Finally, while the v2 spec can be used very effectively with
+distributed storage systems like Amazon S3 or Google Cloud Storage,
+there is room for improvement, particularly regarding how metadata is
+stored and organised.
+
+## Zarr v3 design update
+
+I you are interested in knowing more about the current status of work
+on the v3 spec, please take a look at the [v3 design update
+slides](https://zarr-developers.github.io/slides/v3-update-20190619.html). The
+slides use reveal.js and have both horizontal and vertical
+navigation - if you haven't seen that before, then navigate downwards
+first wherever you can, before navigating to the right.
+
+As I mention in the slides, the current v3 spec is just a straw man,
+meant to illustrate some ideas and potential solutions, but everything
+is up for discussion. So if you have any comments or ideas, please do
+get in touch, anyone is welcome to participate.
+
+----
+
+Blog post written by [Alistair Miles](https://github.com/alimanfoo).