Confusion about hard drive size of with random_split)

I created a class that inherits from and split it using, [TRAIN_SIZE, TEST_SIZE]).
Afterwards I load it via the interface and finally save it using to the hard drive.

dataset = DataSetClass(df=DATA, transform=transform, device, window=3)

DATASET_LENGTH = len(dataset)

train_dataset, test_dataset = random_split(dataset, [TRAIN_SIZE, TEST_SIZE])
dataloader_train = DataLoader(dataset=train_dataset, batch_size=1, shuffle=False, num_workers=4)
dataloader_test = DataLoader(dataset=test_dataset, batch_size=1,  shuffle=False, num_workers=4), "/path/to/"), "/path/to/")

However the saved files are of the same size on the hard drive, why is that?

I think, PATH) would try to pickle and store the actual Python DataLoader object without the internal data, as e.g. your Dataset could load the actual samples lazily, so you might want to store the real DATA object instead of the DataLoader wrapper.

Thank you for your reply!
I will look into that.