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Linux Not Quite Ready For New 4K-Sector Drives
Theovon writes "We've seen a few stories recently about the new Western Digital Green drives. According to WD, their new 4096-byte sector drives are problematic for Windows XP users but not Linux or most other OSes. Linux users should not be complacent about this, because not all the Linux tools like fdisk have caught up. The result is a reduction in write throughput by a factor of 3.3 across the board (a 230% overhead) when 4096-byte clusters are misaligned to 4096-byte physical sectors by one or more 512-byte logical sectors. The author does some benchmarks to demonstrate this. Also, from the comments on the article, it appears that even parted is not ready, since by default it aligns to 'cylinder' boundaries, which are not physical cylinder boundaries and are multiples of 63."
About the microcode part. The drive pretends to be a 512byte drive, but internally is using 4k sectors and and claims to 'translate transparently'. I can understand that in a random-access scenario it it has to read-modify-write 2 sectors each time and performance suffers (2 additional reads and one additional write). But in a sequential access scenario, the penalty should be once per sequence/file, not once per sector. Here the microcode fails completely to make the best out of the suboptimal situation.