Sure, but this ignore the discussion in the Ars article of the penalty: RMW (read, modify, write). Quoting from the Ars article:
"And so it was that last September (and it's this that makes it a little surprising that the BBC and other outlets are talking about the issue now, but it's one that certainly deserves the publicity), Western Digital announced its "Advanced Format" drives. Advanced Format drives use the 4096-byte sectors, 100-byte error codes, and a 40-byte gap as described above. However, to maintain compatibility with Windows XP, they pretend to use 512-byte sectors. As can be seen from the spec sheet (the drives with 64 MiB cache, model numbers ending in AARS or EARS) all use 4096 byte sectors internally) the sector counts even for the 2 TB drives are high; the 2 TB disk having just shy of 4 billion sectors. This kind of deceit is a problem if software tries to write less than 4096 bytes at a time. To write 512 bytes out of 4096, the drive must read all 4096, update the 512 written bytes, and then write back all 4096 bytes (a process known as read-modify-write, RMW). That means more seeking and more disk activity, which is clearly going to perform worse than a 512 byte write on an old drive with true 512 byte sectors. But this isn't such a problem since, as already mentioned, most disk activity occurs in multiples of 4096 bytes anyway. When writing 4096 bytes, the RMW cycle isn't needed, as there's no need to read data if it's going to be overwritten anyway, so the performance impact is negligible. The biggest problem is when the 4096 byte write straddles two sectors. When that happens, the situation is even worse as two RMW cycles are needed, one for each partially-written sector. However, as long as the partition starts on sector boundary, "almost all" subsequent writes will-due to the OS's widespread use of 4096 byte writes-line up properly, so they won't straddle multiple sectors and won't need read-modify-writes. And as luck would have it, the most widely used operating system in the world will always create partitions that don't line up nicely. Single partition Windows XP systems will always make the first partition start on the 63rd 512 byte sector. If it was just one sector further on, then everything would line up nicely on these pseudo-512 byte sector drives. But as it is, Windows XP partitions on such a disk will have to suffer two RMW operations for almost every single write made to the disk. This is mitigated somewhat by many operations being multiples of 4096 bytes, so it's only at the start and end of each operation that the read-modify-write is needed, but nonetheless the overhead is substantial." Thank you, Mark Snyder -----Original Message----- The 512-byte sectors are emulated. That's what the OS sees. Physically, they're 4K sectors. ************************************************************************* ** List info, subscription management, list rules, archives, privacy ** ** policy, calmness, a member map, and more at http://www.cguys.org/ ** *************************************************************************
