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12Gb/s SAS Seagate 6TB Enterprise Capacity 3.5 HDD v4 Review

By: Paul Alcorn | HDDs in IT/Datacenter | Posted: Jun 28, 2014 10:50 am
TweakTown Rating: 93%Manufacturer: Seagate

Seagate 6TB Enterprise Capacity 3.5 HDD v4 Internals




The 12Gb/s SAS Seagate Enterprise Capacity 3.5 HDD v4 comes in the 3.5" form factor. The breather hole to the upper left of the Seagate logo reminds us of the v4's standard drive architecture. The Seagate v4 has a humidity sensor that detects when the drive is above spec and alerts the user. The v4 features ramp load technology and a top-cover attached motor.




The foam covering rests between the PCB and the drive to absorb vibration. Thermal pads cover the controller and motor controller to shed heat into the case of the drive. There is a sheer plastic cover over three rows of capacitors on the right edge of the PCB.


Most importantly there are two big mounting pads on the slender end of the PCB. The PCB for the SAS version of the 6TB Seagate is longer on this portion of the PCB, and the SATA version does not have these mounting pads. One pad, the X shaped pad on the end, is undoubtedly for a NAND package, indicating a strong likelihood of a future SSHD version of this drive. The square pad next to it is likely for an additional controller for NAND management, especially in light of the PCB traces routing from the NAND package directly to the adjacent mount points.


The previous Turbo SSHD from Seagate utilized the standard drive controller for caching operations, but bringing another controller onto the drive would offer much more performance, and also more robust caching and tiering algorithms. Using the same controller for drive and NAND operations remains quite the feat but this could become more challenging with more NAND capacity. Management of more LBA's requires more FTL (Flash Translation Layer) horsepower, and it is doubtful there will be the inclusion of an additional cache chip for LBA mapping purposes. A SandForce controller variant would make a great fit for this architecture because they do not require DRAM caching for LBA management. An additional DRAM chip would be difficult due to space and power constraints.


Seagate just purchased SandForce from Avago recently, but Avago had just purchased SandForce from LSI, who also happens to manufacture the other controller on this HDD. We expect some integration of the product stacks in the future, and this could have been just one more reason for Seagate to pick up SandForce. Of course, this is all wild speculation and Seagate has not confirmed a SSHD version.




This image is from the Seagate Turbo SSHD article we posted a few months ago. Seagate used the PCB from the standard 15K HDD (on the left) with the same X shaped NAND mounting pad, but added a NAND package for the SSHD version (on the right). This at least confirms the same NAND mounting scheme.




The LSI TT50692 controller sets next to the 128MB Winbond multi-segmented cache module.


The SK Hynix memory chip offers 128MB of multi-segmented cache. The SMOOTH drive motor controller resides to the bottom of the PCB. Two accelerometers occupy opposing sides of the PCB to detect and help counteract drive movement and vibration. The Seagate v4 touts industry-leading rotational vibration tolerance.




Idle power consumption is a pain point in the datacenter. The Seagate Enterprise Capacity v4 utilizes PowerChoice Technology. PowerChoice provides 4 enhanced idle modes that place the drive into deeper quasi-sleep cycles to conserve power. In a typical implementation, the feature is enabled with a SAS Mode Page or SATA Set Feature command. Once enabled, PowerChoice places the drive into successively deeper idle states triggered by the length of drive inactivity. There is also the option for immediate host-initiated power transitions with SAS/SATA commands. Each consecutive sleep mode requires more time for resumption. We test idle power consumption without PowerChoice activated, so there is an option for even lower idle power consumption.


We tested idle power and measured the SAS v4 at 9.8 Watts, the SATA v4 at 9.1 Watts, and the He6 at 7 and 5.4-5.5 Watts during deeper sleep intervals. SAS typically consumes more power than SATA, so the higher power draw is expected. SAS is a dual-port full-duplex connection that allows read and write activity simultaneously, resulting in the higher power draw.



Seagate v4 Specifications


The Seagate v4 comes in 4KN and 512E flavors, and offers SED models (AES-256) with ISE (Instant Secure Erase). ISE eases drive retirement and repurposing by eliminating the need for physical destruction. Seagate SED drives are typically the same price as standard drives. There is also an SED-FIPS 140-2 model available. The SED-FIPS version is only available at the 6TB capacity point. Seagate is the only drive manufacturer that offers SED-FIPS drives with tamper-evident coverings.



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