What is the --db-sync-mode option in monerod?

--db-sync-mode tells monerod, the Monero node program, how to save its blockchain database to disk. It controls the balance between disk performance and protection against crashes or power loss—not how quickly new Monero blocks are created.

What “sync” means here

Your node keeps a local database of the blockchain: Monero’s shared record of transactions. As it downloads and checks blocks, it adds information to that database.

Writing information and making sure it has reached durable storage are not always the same thing. Your operating system can temporarily hold writes in memory before sending them to disk.

Here, “sync” means making database changes durable on disk. That is different from blockchain synchronization, which means catching your node up with the network. This option can affect how quickly that catch-up runs, but it does not change which blocks your node checks or accepts.

How the setting is written

The option uses this general format:

--db-sync-mode MODE:METHOD:INTERVAL

Its parts mean:

• Mode — safe, fast, or fastest: Chooses the database’s safety and performance settings. safe prioritizes durability, while the faster modes relax safeguards to reduce disk work.
• Method — sync or async: For modes that use scheduled database syncing, this controls whether the node waits for the sync operation or lets it run in the background.
• Interval — a number followed by blocks or bytes: Sets how much blockchain work accumulates between scheduled sync operations.

These parts work together; they are not three completely independent switches. In particular, safe uses the database’s safer write behavior rather than relying on the periodic schedule used by faster modes.

A commonly shipped default is:

--db-sync-mode fast:async:250000000bytes

That uses fast mode, background syncing, and a byte-based threshold of roughly 250 MB. Check monerod --help for the default in your installed version.

Which setting should you choose?

If you are unsure, keep your version’s default. It is intended to provide a practical balance for ordinary node operation.

For a more conservative choice, you can start your node with:

monerod --db-sync-mode safe

This may make database-heavy work slower, especially during the first blockchain download.

Treat fastest as a deliberate trade-off, not a free speed upgrade. After an unexpected shutdown, less conservative settings can leave recent changes missing or the database needing recovery. In a worse case, you may need to download the blockchain again.

Always shut down your node normally. No setting can fully protect against faulty storage or hardware that mishandles disk writes.

What it means for solo mining or P2Pool

This setting belongs to your node, not your mining software. It does not directly raise your hashrate, the number of mining calculations your device performs each second.

For solo mining or P2Pool, the useful goal is a healthy node that stays current and responds reliably. Changing database settings will not improve your mining odds unless it resolves a genuine node-performance problem.

The bottom line

Leave --db-sync-mode at its default unless you have a specific reason to change it. Choose safe when stronger database durability matters more to you than write performance.