SAS-3 vs SAS-2 HDDs

HP's published drive specs on their SAS drives seems to indicate there is a difference in the seek times on the drives:

HP 146GB 3G SAS 15K 3.5" DP ENT HDD

Transfer Rate Synchronous (Maximum) 3 Gb/sec
Seek Time (typical reads, including settling)

• Single Track 0.57 ms

• Average 3.5 ms

• Full-Stroke 9.0 ms

HP 146GB 3G SAS15K SFF (2.5") DP ENT HDD

Transfer Rate Synchronous (Maximum) 3 Gb/sec

Seek Time (typical reads, including settling)

• Single Track 0.14 ms

• Average 2.58 ms

• Full-Stroke 4.85 ms

So 2.5" seems quite a bit quicker on the seek times. You also wanna be mindful that the new drives come with the 6G SAS interfaces which are more rapid then the 3G interfaces, but the disk controller has to support it (such as the P410's you get in HP DL G6 servers after a firmware upgrade).

The "SATA = 7.2K RPM, SAS = 10/15K RPM" mind-set is strong, and (in my opinion anyway) where most of the "SAS is faster than SATA" thinking comes from. There are some slight differences between SAS and SATA drives, notably in their on-board caching algorithms (NCQ vs. TCQ). However, the performance difference of equivalently specced hard-drives will be fractional percentage points in most use-cases.