Command Duration Limits (CDL) - Improving IOPS per TB in HDDs

Learn about Command Duration Limits (CDL), a Quality of Service protocol for SCSI and ATA HDDs that enables drives to optimize command execution through traffic classes and duration policies. Explore the two-dimensional CDL behavioral model that allows hosts to set command priorities through Duration Limits and guide device behavior with Duration Limit Policies as commands approach their limits. Discover how CDL has been standardized across SCSI and ATA implementations and adopted by drives, the Linux kernel, and SAS hardware ecosystem, with potential adaptation for NVMe HDDs. Examine real-world performance results demonstrating CDL's impact on command tail latencies and the performance trade-offs involved in maximizing IOPS per TB in high-capacity HDDs. Gain insights into the current state of CDL support across software and hardware ecosystems through practical examples and field implementation data presented by industry experts from Western Digital.