Disk can lie to you when you write to it

I’ve seen disks do off track writes, dropped writes due to write channel failures, and dropped writes due to the media having been literally scrubbed off the platter previously. You need LBA seeded CRC to catch these failures along with a number of other checks. I get excited when people write about this in the industry. They’re extremely interesting failure modes that I’ve been lucky enough to have been exposed to, at volume, for a large fraction of my career.

I thought an fsync on the containing directories of each of the logs was needed to ensure the that newly created files were durably present in the directories.

> Conclusion

> A production-grade WAL isn't just code, it's a contract.

I hate that I'm now suspicious of this formulation.