public Set<String> findPartitionsOnDisk(DiskId disk) {
    Set<String> partitionDirs = new HashSet<>();
    File mount = new File(disk.getMountPath());

    if(mount.exists() && mount.isDirectory())
    {
      File[] ambryDirs = mount.listFiles(File::isDirectory);
      if(ambryDirs != null)
      {
        for(File dir : ambryDirs)
        {
          // Tommy: If we store just the leaf name from File.getName() will that work
          //        when comparing with the directory names we get from ReplicaId??
          //        AmbryPartition::toPathString() returns the partition ID as a string.
          String dirName = dir.getName();
          if(looksLikePartition(dirName))
          {
            partitionDirs.add(dirName);
          }
        }
      }
    }
    return partitionDirs;
  }
Find all the partition directories on the disk.
@param disk an instance of DiskId to search for partition directories.
@return A {@code Set} of partition directories on the disk. The set will be empty if no partition
       directories are found, or if something goes wrong (e.g. mount path does not exist).
ambry-store/src/main/java/com/github/ambry/store/PartitionFinder.java