2.5 Admins 2.5 Admins 287: Dual Arguators
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Feb 19, 2026 They argue over how dual-actuator hard drives will really behave and what that means for filesystems. They debate drive-managed versus host-managed approaches and whether firmware can predict access patterns. They weigh real-world IOPS gains, niche datacenter uses, and consumer trade-offs. They also cover setting up ZFS native encryption on laptops and strategies for offsite encrypted backups.
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Dual-Actuator Drives Face Filesystem Reality
- Dual-actuator HDDs aim to increase IOPS by splitting work between two head assemblies, but filesystem/layout interaction complicates real gains.
- Existing OS behavior and write patterns can leave one actuator idle, limiting practical performance improvements.
Drive-Managed Mapping Mirrors SSD Controllers
- Treating a dual-actuator HDD like an SSD means using a virtual sector map and drive-managed mapping to expose parallelism.
- Zone/host-managed approaches already exist in SSDs and SMR that the drives can reuse for parallelism.
Heuristics Can Unlock Partial Parallelism
- Firmware can heuristically split writes between actuators based on concurrent pressure and virtual LBA patterns.
- Perfect layout for reads is unlikely, but heuristics may yield materially better results than nothing.
