@Override
  public List<DiskId> getDiskIdsToHydrate() {
    List<DiskId> diskIds = new ArrayList<>();
    runningThreads.forEach((diskId, fileCopyThreads) -> {
      if (fileCopyThreads.size() < numberOfThreadsPerDisk) {
        diskIds.add(diskId);
      }
    });
    return diskIds;
  }
Identifies disks that have capacity for additional threads.
Returns a list of disk IDs where the number of running threads
is less than the maximum allowed threads per disk.
@return List of disk IDs that can accommodate more threads
ambry-file-transfer/src/main/java/com/github/ambry/filetransfer/DiskAwareFileCopyThreadPoolManager.java