Hello self-hosters! :) I'd like to tap into your experience
tl;dr: Is it really a bad idea to use MariaDB with data over NFS?
My setup
- RAID NFS NAS on RPi4
- "CPU machine", just an old laptop for now
The idea is that NAS stores the data and RAID mitigates single point of failure. Laptop is only for running the stuff, all docker-compose are under git, uploaded elswhere. Laptop fails - I buy a new refurbished one and put everything back together from data on NAS and git
Problem
But Nextcloud uses DB. ATM it sits on the laptop. And I'm thinking how to somehow move that data to the NAS.
At the beginning NAS was just for NC files, connected as NC "external storage" over SFTP. But there were issues with this setup and NFS4 turned out to not require Kerberos to work.
Since NFS docker volumes have been working quite fine, I thought about just moving the data to the NAS. But then I read this:
Generally, we recommend not to use NFS (Network File System) with MariaDB, for these reasons:
MariaDB data and log files on NFS volumes can become locked and unavailable for use. Locking issues may occur in cases where multiple instances of MariaDB access the same data directory, or when MariaDB is shut down improperly, for instance, due to a power outage. In particular, sharing a data directory among MariaDB instances is not recommended.
Data inconsistencies due to messages received out of order or lost network traffic. To avoid this issue, use TCP with hard and intr mount options.
And I feel discouraged
- I could move whole DB (I mean including the process) to the NAS, but then operating the DB becomes NAS' burden and breaks the responsibility separation
I'm not a fan of this idea - I could treat NAS as first stage of backup for that DB data and just send the data to NAS once a day
Also a bit meh. Getting back up from server failure will require copying the data - Maybe it's not that bad to use MariaDB with NFS?
If there is a problem with server-NAS connection, I actually don't want Nextcloud to work at all. It should fail, so I know I need to fix something
So, what are your experiences? Is running the DB on one machine, using the data from another machine over NFS a shot in the foot?
Yeah, but if that setup leads to problem in a few months, I won't catch that. That's why I decided to ask and judging by the other answer, I dodged a bullet here
Now I'm thinking of setting up something like this. Maybe even in another container? One volume with data bound, one with NFS and a bunch of scripts in entrypoint to rsync(?) between the two on inotifywait. There is lsyncd but it's been unmaintained for two years now
I know it has been 3 days since you posted buy why not set up replication in the database it self? Sounds like you're over complicating replication.
I run in k8s but I have a database with local disk, and I have another cronjob that takes a backup into the first database docker init folder. Older backups end with -date so they won't get picked up by the init script. You can do similar with just docker.
I'll echo everyone else. Database need local disk. I speak from experience of doing it over NFS. Even containers that have a hidden sqlite3 database should get local disk.
AFAIK db replication would require running another db on NAS. Which I tried to avoid
Yeah, that's why I'm thinking to do. Have a container that watches changes to db data and rsyncs those into the NAS for safekeeping. My main goal in all of this is so db data won't die with laptop's SSD
I think the inode rsync is a bad idea. The 2nd DB would be on the NAS but its not being used by the app, so as long as it's asynchronous writes, you should be okay.
In either case, I hope you have backups, not just the copy