What is TrueNAS writing all the time to disk?
What is TrueNAS writing all the time to disk?
I have a TrueNAS install with SMB turned on and nothing else. Even when it’s idle and nothing is accessing it, there’s constant disk activity. Very low bandwidth, but it’s like some log is in verbose mode.
TrueNAS is installed in a NVMe disk with plenty of room, and there’s only one pool. I’ve checked my snapshot configuration, nothing enabled faster than daily.
What could be causing it? How do I stop it or redirect it to the NVMe drive? I’m willing to create a partition on the NVMe drive if that’s what will do it.
Edit: thanks everyone for all the feedback, I’ll try these out and report back.
That's most likely the syslog. Check the settings, you can choose the volume to use for it.
Or set up a ramdisk, or turn off log to disk entirely somehow. But if you do that, you'll lose logs between reboots or crashes, making troubleshooting harder.
Dirty secrets about you.
Have you run
lsof? See also: https://www.brendangregg.com/linuxperf.htmlEvery 4-5 seconds? Yeah, logging.
You can either move the system dataset to your boot drive/pool or syslog to /var/log:
https://www.truenas.com/docs/core/coretutorials/systemconfiguration/settingthesystemdataset/
I've seem many users recommend a reboot after changing those settings.
If it’s logs, there’s a package called log2ram - it’s designed for small form factor systems to reduce writes to SD cards but does apply anywhere you want to log but not hit disk immediately. It syncs logs to disk on a regular basis so you don’t lose much if the system crashes.
Ooh that sounds promising, thank you!
Probably these directories...
/tmp /var/tmp /var/log
Two are easy to migrate to tmpfs if you are trying to reduce disk writes. Logs can be a little tricky because of the permissions. It is worth getting it right if you are concerned about all those little writes on an SSD. Especially if you have plenty of memory.
This is filesystem agnostic btw so the procedure can apply to other filesystems on Linux operating systems.
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