关于disk_optimization_strategy配置项功能及场景选型的咨询

Great question—let’s break down everything you need to know about the disk_optimization_strategy configuration option, including validating your smart speculation.

This config is designed to optimize I/O operations based on the underlying storage medium's inherent performance characteristics. It lets the system tailor how it handles read/write requests to get the best possible throughput and latency from either solid-state drives (SSD, the default) or traditional spinning hard disk drives (HDDs).

Your guess is spot-on—here’s the exact breakdown:

• SSD mode (default): Leverages SSDs' strength in random I/O (no moving parts like disk heads). It processes smaller data blocks with immediate, unbatched operations, since SSDs don’t suffer the latency penalty of repositioning heads for small requests.
• Spinning mode: Optimized for mechanical HDDs, where disk head movement is the biggest performance bottleneck. This mode queues multiple small write requests, batches them into larger chunks, and then writes them all at once. This minimizes how often the disk head has to reposition, drastically improving throughput and reducing latency variability for sequential workloads.

1. Spinning disks with an SSD cache layer #

In this hybrid setup, focus on the persistent storage layer (the spinning disks), since the SSD cache is typically handling hot, random I/O while the HDDs store cold data or handle background syncs. Set disk_optimization_strategy to spinning:

• The batch-write optimization will align with the HDDs' limitations, reducing head movement overhead for the data that eventually lands on the mechanical disks.
• Even if the SSD cache handles most front-end I/O, the background writes to HDDs will benefit from the batching logic.

2. SAN storage (despite being unrecommended) #

First, note that official guidance discourages using SAN for this workload, but if you have no other choice:

• If the SAN’s underlying storage is mechanical HDDs: Use spinning mode to align with the disk head movement constraints—your SAN may already do some batching, but this config adds another layer of optimization tailored to the medium.
• If the SAN uses SSDs under the hood: Stick with the default SSD mode to take advantage of the random I/O performance of SSDs.

Your initial speculation about the modes is 100% correct—this config’s core is adjusting I/O batching behavior to match the storage medium’s strengths and weaknesses.

内容的提问来源于stack exchange，提问作者Jason Nethercott