Regarding unsafe-no-fsync, a middle ground?

[RaymiiOrg]

If the config option unsafe-no-fsync is enabled, is there still data saved to disk? For example when the process is stopped?

I'm looking for a middle ground, where my storage is not trashed by writes continuously but for example, every 5 minutes. (Slower harddisks).

By enabling unsafe-no-fsync, is there still data saved but is the operating system in control of when that's synced to disk?

I'm aware of the possibility of data loss and inconsistencies, but those are okay.

[kien-truong]

etcd/server/storage/wal/wal.go

Line 800 in 94077fc

func (w *WAL) sync() error {

Yes, the data is still flushed, but no fsync is called, which means it's up to the OS kernel to decide when the data is synced to disk.

[akalenyu]

So this configurable is just about WAL? What about the actual commit of the key value data (not the log) to the disk? That keeps getting fsync'd by etcd?

[kien-truong]

When you use unsafe-no-fsync, the backend (boltdb) is also set to operate in NoSync mode, so it'll not issue any fsync when writing data to disk either

etcd/server/storage/backend/backend.go

Line 192 in bf63f91

bopts.NoSync = bcfg.UnsafeNoFsync

[akalenyu]

Thank you! So this configurable is both about the WAL log writes & actual data writes not being followed by an fsync?