opening a zarr dataset taking so much time with dask
Open
topic-dask
topic-performance
topic-zarr
upstream issue
- Dominant language
- Python
- Stars
- 4.2k
- Forks
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- Avg merge
- 2d 15h
- Merged PRs (30d)
- 14
Description
What is your issue?
I have an era5 dataset stored in GCS bucket as zarr. It contains 273 weather related variables and 4 dimensions. It's an hourly stored data from 1940 to 2023.
When I try to open with ds = xr.open_zarr("gs://gcp-public-data-arco-era5/ar/full_37-1h-0p25deg-chunk-1.zarr-v3") it takes 90 seconds to actually finish the open call.
The chunk scheme is { 'time': 1 }.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Reproduce the reported call through xarray.open_zarr using the provided GCS Zarr URL and the stated time-only chunking, then profile where the 90-second open time is spent. Review the linked pull request for the current work; completion would require an agreed, measured improvement to dataset opening time.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- data, performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100