Analysis: The Impact Of Shifting From 512 Byte To 4 KB Sectors

Analysis And Conclusion

We found that the new 750 GB Toshiba MK7559GSXP is at least a match to its predecessor, the 640 GB MK6465GSX in all low-level benchmarks. It is comparable in I/O performance and access time, and it even provides much improved throughput performance. However, our PCMark Vantage application test shows decreased performance for the new drive with its 4 KB sector size in popular Windows scenarios. What’s the best choice, then?

The low-level performance numbers show that the 4 KB sector drive is performing as expected, and that the reason for the PCMark Vantage results has to be found somewhere else. We can also be sure that the sector alignment works well because Windows Vista and Windows 7 create partitions accordingly, and because we checked separately.

However, we cannot control the way data writes are actually executed and organized. In the case of PCMark Vantage, the benchmark was never tweaked to minimize the number of smallest-size write requests in favor of larger chunks of data. If you write large files to the hard drives, then the new 750 GB drive wins--despite and because of its 4 KB sectors being smaller than the write request. But as long as applications hammer smaller data write requests onto an advanced format drive in 512 byte legacy mode, we’ll see performance impacts here and there, just because each write operation consists of Read-Modify-Write, which involves a full 4 KB sector with all of its eight, legacy 512 byte chunks.

This becomes more of an issue if more random write activity is involved, and it becomes less of an issue with larger data chunks and sequential operation. In the case of PCMark Vantage, we’re seeing great game performance because it does not involve many writes. Windows Movie Maker and Media Center, however, trigger lots of write activity, and we believe the system executes many write requests that end up being smaller than 4 KB.

Recommendations

Be this as it may, the IDEMA hard drive makers (International Disk Drive Equipment and Materials Association) decided that all new hard drive platforms available in channel markets shall be based on the Advanced Format (4 KB) by January 2011, meaning that the question of whether or not we like this will soon be irrelevant--unless you want to be a rebel and buy an older hard drive model.

The application performance issues we've shown remain. But if you’re using a modern operating system like Windows Vista with SP1, Windows 7, Mac OS 10.4 or up, then you are usually safe. However, you will still have to look for alignment tools if partitions are created by an imaging utility instead of the operating system, or if you run multi-boot environments. In those cases, you’ll have to dig into sector alignment whether you want it or not, or you will face more substantial performance drops.

From the hardware side there is nothing that really speaks against a 4 KB sector drive. Mainstream users will not notice much of a difference, and enthusiasts are always better off putting data onto mechanics disks, and running the operating system and applications off a fast SSD.