SAS Storage: High-Performance Hard Drives

Seagate Cheetah 15K.6

Seagate has always been serious about its Cheetah drive, which represents one of the finest enterprise hard drive families in the industry. We received the latest generation, the Cheetah 15K.6. This is still a 3.5” hard drive, utilizing a SAS/300 or Fibre Channel interface, featuring 16 MB of cache and spinning at a fast 15,000 RPM. While none of this sounds spectacular, the new drive introduces a number of improvements over its predecessors.

Up to 450 GB Capacity

The most obvious improvement is the capacity bump, which was really overdue in light of 1 TB capacities having been available in the desktop space for more than a year, and notebook drives reaching 500 GB. Seagate offers Cheetah 15K.6 drives at 450 GB, 300 GB and 146 GB (4, 3 and 2 discs). The higher capacities were made possible by—you guessed it—perpendicular recording technology, which finally is making an impact in the enterprise space as well.

1.6 Million Hours MTBF

Seagate’s data sheet emphasizes reliability, with a 1.6 million hour mean time between failure figure (0.55% annual failure rate stated), and a 5-year warranty. This, however, isn’t a big deal, as all enterprise-class products are typically covered for five years.

Impressive Performance

While Seagate talks about a maximum sustained transfer rate of 164 MB/s, we actually measured as much as 174.6 MB/s maximum read throughput, and about the same number for writes. Minimum throughput always stays above 100 MB/s, which clearly is a new record for mechanical drives, and equals almost a 40% improvement over the predecessor Cheetah 15K.5 or other 15,000 RPM units. This is actually even more impressive than the maximum throughput.

The average access time of 5.7 ms cannot match the 0.5 ms or less we find with flash SSDs, but this drive still delivers best-of-class access times. In fact, it’s interesting to see that the Cheetah 15K.6 is actually head to head with the 2.5” Savvio 15K.1, which has been the fastest in access time so far.

Disk Encryption as an Option

Seagate offers a full disk encryption (FDE) version of this drive, but it is not going to be available at retail. Instead, Seagate ships these only to some large OEMs. The manufacturer makes some good points about the FDE feature on the data sheet, as it does have more advantages than just plain security, by encrypting files on the fly. For example, drive decommissioning cost can be neglected for FDE drives, as you do not have to carefully erase existing data.