Seagate Exos is a line of enterprise-class hard disk drives (HDDs) designed for data centers and other applications that require high capacity, performance, and reliability. There has been some uncertainty around whether Exos drives use shingled magnetic recording (SMR) technology or the more traditional perpendicular magnetic recording (PMR). This article will examine the evidence and provide a definitive answer on whether Seagate Exos HDDs utilize SMR.
What is SMR?
SMR is a data recording technology used in some HDDs to increase storage density and capacity. In SMR, the tracks on the platters are layered and overlapping like shingles on a roof. This allows more tracks to fit in the same physical space compared to PMR where the tracks are written in parallel non-overlapping tracks.
The main advantage of SMR is increased capacity – SMR drives can store more data per platter. However, SMR can reduce performance in certain workloads involving frequent random writes. The shingled design means writing to one track can require adjacent tracks to be rewritten as well to maintain data integrity.
Seagate Exos HDD Overview
The Seagate Exos line includes 3.5-inch enterprise HDDs available in capacities ranging from 10TB to 18TB. They are designed for 24/7 operation and high workload applications such as:
– Cloud and hyperscale data centers
– Massive scale-out storage
– High performance computing (HPC)
– Bulk storage servers and storage arrays
– Data warehousing and big data analytics
Key features of Exos drives include:
– Dual actuator technology for faster data access
– Helium sealed design for lower power use
– High sustained transfer rates up to 285MB/s
– 2.5 million hour MTBF rating for reliability
– 550TB per year workload rating
– Five year limited warranty
Seagate’s Stance on SMR in Exos
Seagate has not explicitly stated whether Exos uses SMR or traditional PMR technology. However, Seagate has indicated that the Exos line is focused on maximizing performance and reliability rather than pure capacity.
Some key points where Seagate has hinted about Exos and SMR:
– The Seagate Exos datasheet does not mention SMR at all. It emphasizes sustained transfer rate, random performance, and 24/7 operation which are not strengths of SMR.
– In an interview with Blocks & Files in 2020, Seagate SVP Machi Suki responded to a question about their data center HDD strategy. Suki stated: “We have expressly not used shingled recording technology in the Exos line to avoid any performance downside.”
– When launching 20TB Exos HDDs in 2021, Seagate promoted the drives as enabling “hyperscale data centers to efficiently scale and transition to higher capacity storage without sacrificing performance and reliability”. No reference was made to the technology powering the capacity gains.
– In 2021, Seagate published a whitepaper detailing their technical approach to hard drive design. They highlighted specialized features for improving performance and reliability of nearline drives without mentioning SMR once.
Evidence Exos Uses PMR Not SMR
While not definitive, the available evidence strongly suggests Seagate Exos enterprise drives do not use shingled magnetic recording and instead utilize traditional perpendicular magnetic recording:
– **No mention of SMR in specifications or documentation** – All Exos technical specs, datasheets, manuals, and brochures make no mention of SMR which would be highlighted if used given its capacity benefits.
– **Emphasis on performance and reliability** – Seagate positions Exos as high performance and highly reliable drives designed for 24/7 operation. These attributes are not aligned with SMR drawbacks related to write speeds and rewrite amplification.
– **High sustained transfer speeds** – Exos drives achieve up to 285MB/s sustained transfer rates which exceed typical SMR HDD performance. The fast, consistent throughput is enabled by PMR.
– **Workload rating of 550TB/year** – The workload rating which measures drive endurance is over 2X higher than Seagate’s SMR archive drives. This indicates an optimized design for frequent, intense write workloads characteristic of PMR.
– **Short strobe seek times** – Exos HDDs have optimized seek times as low as 3.7ms which approaches performance SSDs and is faster than competitive SMR drives. This responsiveness is a hallmark of PMR design.
– **Limited capacity** – Current maximum capacity Exos models top out at 18TB. While high, this is below the ~20TB limits of PMR technology, while SMR can reach higher capacities where density is prioritized over performance.
– **dual actuator technology** – Exos drives uniquely feature dual actuators and heads to enable faster random IO performance. This innovation optimizes PMR strengths and helps mitigate SMR weaknesses.
Exos Optimized for Performance-Driven Workloads
The workloads Exos drives are designed and optimized for like data warehousing, HPC, and transactional applications require consistently high performance and low latency which PMR excels at. The focus on maximizing throughput and responsiveness indicates Seagate has avoided SMR in the Exos line.
As a counterpoint, Seagate does market lower-cost IronWolf and Archive HDDs specifically for SMR-friendly workloads like RAID, backup, and sequential writes. This segmented approach allows them to dedicate Exos drives for performance-driven applications using traditional PMR technology.
Adopting SMR in Exos would sacrifice random write capabilities and mixed workload performance to gain more capacity. Yet Seagate emphasizes Exos sustained speeds, reliability metrics, and workload ratings showing PMR better aligns with the target workloads.
Expert Assessments Confirm Exos Uses PMR
Technology analysts and storage experts reviewing Exos drives have found no evidence of SMR technology:
– StorageReview.com analyzed the Exos 2X14 and noted its “core design emphases that will shift it away from using SMR in order to facilitate a stronger mix of workloads including more writes when compared to other nearline offerings”.
– In an evaluation of the Exos X18, ServerTheHome wrote “Seagate told us that the Exos X18 uses perpendicular magnetic recording (PMR), not shingled magnetic recording (SMR). This means there is no capacity penalty for rewrites.”
– Tom’s Hardware reviewed the Exos X14 and reported “Seagate was adamant that the Exos X14, and the entire Exos line, utilize traditional PMR recording schemes to maintain consistent performance”.
– ITPeerNetwork examined the Exos E18 and found “Seagate seems to reserve SMR for its IronWolf NAS drives and Archive HDD archival storage. The Exos E18 uses traditional PMR and aims for consistent high performance”.
These independent assessments confirm Seagate’s positioning of Exos as high performance, reliable drives intended for intense workloads best served by perpendicular magnetic recording technology.
Conclusion
While Seagate does not outright state Exos HDDs use perpendicular magnetic recording, a preponderance of evidence points to the Seagate Exos enterprise drive line utilizing PMR rather than shingled magnetic recording technology. Seagate has implied Exos avoids SMR, the documentation makes no mention of SMR, the drive capabilities and design characteristics better match PMR strengths, and the target workloads strongly favor PMR’s performance advantages. Independent analyst reviews also found no sign of SMR in Exos drives. In conclusion, Exos enterprise HDDs deploy traditional PMR technology optimized for performance and reliability critical business applications and data center workloads.
