After setting up local net and the CLI-tool as described in the docs, adding ("applying config to") a small file as described in the docs fails.

Reproduce:

setup localnet and pow cli like described in the docs. Create a small file, create a user, stage the file and apply the config like this:

echo "test" > testfile
response=`pow admin user create`
token=`jq -r '.[] | .token' <<< $response`
export POW_TOKEN=$token
response=`pow data stage testfile`
cid=`jq -r '.cid' <<< $response`
pow config apply --watch $cid

And it will fail with this job status:

JOB_STATUS_FAILED executing cold-storage config:
 making deal configs:
 getting miners from minerselector:
 getting miners from reputation module:
 not enough miners satisfy the miner selector constraints 

When altering the code a bit to return an error as soon as one miner does not satisfy the constraints you learn that the piece size is too small:

JOB_STATUS_FAILED executing cold-storage config:
 making deal configs:
 getting miners from minerselector:
 getting miners from reputation module:
 skipping cached miner, not replying to miner proposal query:
 miner doesn't satisfy piece size constraints:
 256<128<536870912       

When trying to add a bigger file, everything works.

This may leave new users puzzled for a while.

Maybe adding a hint about the file size to the docs would be helpful enough.
Or maybe doing something with this error in reptop.go line 97

if err != nil {
	continue // Cached miner isn't replying to query-ask now, skip.
}

The current handling might also be disadvantageous in other situations: if you have chosen impossible miner requirements, it would be good to know, what requirements exactly is hard to satisfy.

I have a solution in mind and will follow up with a pull request.