What causes MySQL doublewrite buffer contention?

Rapid dirty page accumulation in InnoDB buffer pool during sync flushes, often from CMS metadata writes like WordPress postmeta. Shared storage with async workloads worsens it.

How to diagnose MySQL I/O stalls with blktrace?

Run blktrace -d /dev/nvmeXnY -o trace; blkparse -i trace. Hunt C-Q latencies on ib_doublewrited and high dispatch queues.

Does NVMe prevent MySQL buffer pool contention?

No — IOPS saturation from sync doublewrite hits even NVMe. Tune pool size, dirty pct, and separate storage.

☁️ Cloud & Databases

WordPress Images Spike MySQL's Doublewrite Buffer: 85ms Waits on NVMe Exposed by Blktrace

85 milliseconds. That's what a screaming-fast NVMe drive handed MySQL during a routine image upload. Blktrace cracked open the doublewrite buffer nightmare.

Open Source Beat Apr 11, 2026 4 min read

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iostat output showing MySQL doublewrite buffer contention spike on NVMe during WordPress image processing

⚡ Key Takeaways

Full buffer pools force sync dirty page flushes, bottlenecking doublewrite buffer 𝕏
Shared NVMe storage turns async image writes into DB stalls — isolate workloads 𝕏
Blktrace + iostat + InnoDB status = unbeatable I/O autopsy 𝕏

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#I/O contention #InnoDB #InnoDB doublewrite #InnoDB tuning #MySQL #MySQL InnoDB #MySQL performance #NVMe I/O #WordPress #WordPress optimization #blktrace #blktrace analysis #doublewrite buffer

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Originally reported by Dev.to

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