Seagate Exos 2X14 hard disk drives (HDDs) have 14 TB capacity with Mach 2 dual stage actuators. The two actuators transfer information independent of each other within a single HDD. Within the drive the top half of the write/read heads are attached to one actuator and the bottom half are attached to a second actuator. This parallel access allows higher/input output performance per second (IOPS) close to twice that of a conventional single actuator HDD.
Seagate Mach 2 Dual Actuator HDD
Seagate Product Visualization
Microsoft has been working with Seagate to qualify these Mach 2 drives in their cloud data center operations. They have contributed in testing early Exos 2X14 engineering development units and have now tested Seagate’s Exos 2X14 CTUs (early customer test units). Microsoft reports that they are getting close to twice the throughput and IOPS with these drives than with conventional single actuator HDDs. The Exos 2X14 Mach 2 drives had dual LUNs with a serial SCSI (SAS) interface.
An important reason for cloud providers to adopt dual actuator HDDs is provide a required IOPS per terabyte (IOPS/TB) requirement at a particular latency (time to data). Meeting this requirement makes these drives more attractive for applications including content delivery networks (CDNs), video streaming, mail servers, backup/shuttle servicers, Hadoop, and other cloud applications. Note that the lower cost per TB for HDDs makes them preferable to SSDs for applications with large storage capacities as long as IOPS and latency requirements are met.
If an HDD meets or exceeds the IOPS/TB required by a customer and application, all of the capacity on the HDD can be utilized. If the IOPS/TB on the HDD drops below a threshold determined by the application, the customer cannot utilize all of the drive capacity for the required workload. This then leads to unused capacity for that application on the HDD, referred to as “stranded capacity.” Using a dual actuator Mach 2 drive, the entire HDD can provide the required IOPS/TB and no capacity on the drive is “stranded.”
Using dual stage actuators make all of the storage on the HDD accessible for more applications and will help achieve higher capacity hard disk drives, which results in more storage capacity in a given HDD footprint. Technologies like dual actuator HDDs will help enable 20+ TB HDDs. Furthermore dual (2) actuators are not the limit, 4-actuator drives are envisioned that could provide close to 4X the performance of a single actuator drive.
With possible HDD storage capacities of 40+ TB possible within the next decade, this could keep back end test and burn-in times at reasonable levels and provide the needed IOPS/TB required by many data center applications. Reducing back end test time will also help reduce the cost of the HDD unit, enabling even lower $/TB HDD prices.
A recent release from Microchip about their latest Serial Peripheral Interface (SPI) EERAM memory products shows some of the competitive pressures for emerging memory niche applications.
Microchip 1 Mb EERAM Introduction
Microchip Product and Applications
EERAM is a standalone nonvolatile RAM memory that uses the same SPI and I2C protocols as serial SRAM. This enables devices to retain SRAM content during power loss without using an external battery. When power starts going away data is automatically transferred to the non-volatile memory and it moves back to the SRAM when power is restored.
EERAM is available at a lower price than emerging non-volatile memories because it is built with high volume CMOS and Flash processes. In particular Microchip points out that Ferroelectric RAM (FRAM) is more expensive and less available. The new Microchip EERAM products offer up to 1 Mb of non-volatile memory with an SPI interface starting at $2.90 each.
HDDs with dual actuators could be an important element in achieving 20+ TB hard disk drives with IOPS/TB performance needed for many data center applications. More conventional non-volatile memories such as EERAM may provide competition for emerging memories for use in niche applications. Moving into these niche applications is an important requirement to move to higher production volumes and lower prices.