Write Intensive Usage

When copying games from your Steam Library or other very large files (>10 GB), you might have noticed that write speeds on your SSD start out at full speed and then drop considerably. The underlying reason is that modern drives have caches that soak up write bursts to improve performance. In the fairly uncommon scenario of writing data that's too big to fit into these caches, the drive will have to write data directly to flash, and it will probably juggle some out of its write cache at the same time as well, which can result in a significant loss of write speed. Newer TLC drives operate part of their capacity in SLC mode for increased performance. This test can reveal the size of that SLC cache.

Testing on this page looks at exactly that scenario. We write a sequential stream of 1 MB blocks to the drive in a single thread, like a typical file-copy operation would do, and measure write speeds twice a second. The drive is fully erased before testing to ensure any caches are emptied. Please note that this test writes a lot of data in a very short time, which is something most consumers will never do.


The Seagate BarraCuda will run at maximum write speed of around 500 MB/s only until 4 GB has written, which means it has a small SLC buffer. However, unlike nearly all other TLC drives, write speeds stay very high even though the drive is writing directly to TLC. With 447 MB/s on average for this huge file write task, the BarraCuda is the fastest SATA SSD in our test group, even rivaling some NVMe drives in this scenario.