The problem comes from the fact that we use the indexBase / indexName as the source to create the directory name (in case that's a directory). So in this implementation and if you use a directory, you would likely do

    directoryProviderRoot + "/" + shard

if you want shards in a subdirectory or

    directoryProviderRoot + "." + shard

not not have this sub directory structure but rather the `.n` or `.tenantid` approach