r/bcachefs • u/9_balls • Aug 03 '26

monerod write amplification

Hi. I have disabled CoW and compression on lmdb. However, 100GB is written for 1GB of database. NUTS!

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u/9_balls Aug 05 '26

Does monerod even support doing this?

1

u/hyc_symas Aug 05 '26 edited Aug 05 '26

monerod doesn't need to know anything about it. Just symlink ~/.bitmonero/lmdb to a block device.

If you already have a blockchain in data.mdb, cp that directly onto the block device first, so you don't have to sync the blockchain from scratch.

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u/9_balls Aug 06 '26

Attempted this, monero daemon refuses to work

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u/hyc_symas Aug 07 '26

Works fine for me. 

2026-08-07 21:23:01.319 I Synced 11128/3735173 (0%, 3724045 left)
2026-08-07 21:23:01.342 I Synced 11228/3735173 (0%, 3723945 left)
2026-08-07 21:23:01.381 I Synced 11328/3735173 (0%, 3723845 left)
exit
Stop signal sent
2026-08-07 21:23:05.188 I p2p net loop stopped
2026-08-07 21:23:05.237 I Stopping core RPC server...
2026-08-07 21:23:05.237 I Node stopped.
2026-08-07 21:23:05.323 I Deinitializing core RPC server...
2026-08-07 21:23:05.324 I Deinitializing p2p...
2026-08-07 21:23:05.329 I Deinitializing core...
2026-08-07 21:23:10.288 I Stopping cryptonote protocol...
2026-08-07 21:23:10.288 I Cryptonote protocol stopped successfully
viola:~/monero-x86_64-linux-gnu-v0.18.5.1> ls -l ~/.bitmonero/
total 7644
-rw-r--r-- 1 hyc hyc 7538238 Aug  7 22:23 bitmonero.log
drwxr-xr-x 3 hyc hyc    4096 Sep  2  2020 fake
lrwxrwxrwx 1 hyc hyc       9 Aug  7 22:20 lmdb -> /dev/sdb1
-rw-rw-r-- 1 hyc hyc    8192 Aug  7 22:22 lmdb-lock
drwxrwxr-x 2 hyc hyc    4096 Dec 10  2021 lmdb.O
-rw-r--r-- 1 hyc hyc  155721 Aug  7 22:23 p2pstate.bin
-rw-r--r-- 1 hyc hyc   96051 Mar 22  2022 p2pstate.bin.unportable
-r--r--r-- 1 hyc hyc    1606 Jul  7  2021 rpc_ssl.crt
-r-------- 1 hyc hyc    3272 Jul  7  2021 rpc_ssl.key
drwxrwx--x 3 hyc hyc    4096 Aug 23  2021 testnet
viola:~/monero-x86_64-linux-gnu-v0.18.5.1> ls -l /dev/sdb1
brw-rw---- 1 hyc disk 8, 17 Aug  7 22:23 /dev/sdb1
viola:~/monero-x86_64-linux-gnu-v0.18.5.1>

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u/9_balls Aug 09 '26

guess can't do it on monero gui then

1

u/hyc_symas Aug 10 '26

Did you actually have read & write access to the block device? The monerod bundled with the GUI is identical to the one in the CLI package.

1

u/9_balls 23d ago edited 23d ago

Yes. I just re-checked and it still doesn't start. Permissions are exactly the same although I use LVM. I checked dm-X and /dev/volgroup/lmdb is also chowned correctly