id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1339921253,I_kwDOAMm_X85P3ZNl,6919,Parallel read with MPI,8100801,closed,0,,,4,2022-08-16T07:19:14Z,2023-09-12T15:16:32Z,2023-09-12T15:16:31Z,NONE,,,,"### Is your feature request related to a problem?

Is it possible to somehow extend xarray to use MPI I/O?

### Describe the solution you'd like

We would need to know the offset from where the actual data starts within the file.
Is there a way of retrieving that?
Disclaimer: I am not an expert of NetCDF format - so, apologies if the question is trivial!


### Describe alternatives you've considered

_No response_

### Additional context

_No response_","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6919/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
577068248,MDU6SXNzdWU1NzcwNjgyNDg=,3842,Mixed datatypes Dataset.to_netcdf(),8100801,closed,0,,,3,2020-03-06T17:16:13Z,2020-03-23T15:12:18Z,2020-03-23T05:38:31Z,NONE,,,,"<!-- A short summary of the issue, if appropriate -->
Not sure if this is intended, but when I try to save a Dataset to netCDF using Dataset.to_netcdf(), it produces the following error: ValueError: could not convert string to float: 'a'

This seems to be due to forcing datatypes to be equal to the datatype of the first column encountered. See below a simple working example.

#### MCVE Code Sample
<!-- In order for the maintainers to efficiently understand and prioritize issues, we ask you post a ""Minimal, Complete and Verifiable Example"" (MCVE): http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports -->

```python
import pandas as pd
import xarray as xr

df = pd.DataFrame()
df['Values' ] = [1.0,2.0,3.0]
df['Strings'] = ['a','b','c']

da = xr.DataArray(df)
ds = xr.Dataset()
ds['A'] = da
ds.to_netcdf('A.nc')

```

#### Expected Output
Gianmarcos-MacBook-Pro-2:examples gian$ python3 test_xarray.py 
Traceback (most recent call last):
  File ""test_xarray.py"", line 11, in <module>
    ds.to_netcdf('A.nc')
  File ""/usr/local/lib/python3.7/site-packages/xarray/core/dataset.py"", line 1232, in to_netcdf
    compute=compute)
  File ""/usr/local/lib/python3.7/site-packages/xarray/backends/api.py"", line 749, in to_netcdf
    unlimited_dims=unlimited_dims)
  File ""/usr/local/lib/python3.7/site-packages/xarray/backends/api.py"", line 792, in dump_to_store
    unlimited_dims=unlimited_dims)
  File ""/usr/local/lib/python3.7/site-packages/xarray/backends/common.py"", line 261, in store
    variables, attributes = self.encode(variables, attributes)
  File ""/usr/local/lib/python3.7/site-packages/xarray/backends/common.py"", line 347, in encode
    variables, attributes = cf_encoder(variables, attributes)
  File ""/usr/local/lib/python3.7/site-packages/xarray/conventions.py"", line 605, in cf_encoder
    for k, v in iteritems(variables))
  File ""/usr/local/lib/python3.7/site-packages/xarray/conventions.py"", line 605, in <genexpr>
    for k, v in iteritems(variables))
  File ""/usr/local/lib/python3.7/site-packages/xarray/conventions.py"", line 241, in encode_cf_variable
    var = ensure_dtype_not_object(var, name=name)
  File ""/usr/local/lib/python3.7/site-packages/xarray/conventions.py"", line 201, in ensure_dtype_not_object
    data = _copy_with_dtype(data, dtype=_infer_dtype(data, name))
  File ""/usr/local/lib/python3.7/site-packages/xarray/conventions.py"", line 160, in _copy_with_dtype
    result[...] = data
ValueError: could not convert string to float: 'a'


#### Problem Description
It should be able to save the file into netcdf format?


#### Versions
<details><summary>Output of `xr.show_versions()`</summary>

INSTALLED VERSIONS
------------------
commit: None
python: 3.7.6 (default, Jan  7 2020, 19:34:32) 
[Clang 11.0.0 (clang-1100.0.33.16)]
python-bits: 64
OS: Darwin
OS-release: 19.2.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: C
LOCALE: None.UTF-8
libhdf5: 1.10.2
libnetcdf: 4.4.1.1

xarray: 0.11.2
pandas: 0.24.2
numpy: 1.16.2
scipy: 1.1.0
netCDF4: 1.4.3.2
pydap: None
h5netcdf: None
h5py: 2.8.0
Nio: None
zarr: None
cftime: 1.0.3.4
PseudonetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: 1.2.1
cyordereddict: None
dask: 0.19.4
distributed: None
matplotlib: 3.0.2
cartopy: None
seaborn: 0.9.0
setuptools: 42.0.2
pip: 20.0.2
conda: None
pytest: 3.8.2
IPython: 7.1.1
sphinx: 1.8.4

</details>
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