Dear NetBSD Community, I am considering gradually migrating all of my systems from Linux to NetBSD, drawn by the simplicity and philosophy of NetBSD. However, I have one concern regarding the default filesystem, FFS2. How resilient is this filesystem in the event of power outages? Some of my servers will be located in a remote area in the central mountains of Spain, where power outages are occasionally caused by storms. Any insights or recommendations on handling these scenarios would be greatly appreciated. Thank you in advance for your advice.

@"htorrado"#p18075 There is an old deficiency in FFS called "garbage data appended on write". This happens if power is lost in the middle of writing a file - the file size is updated before its contents, leading to garbage being appended to the end of the file. WAPBL unfortunately makes this worse because it has better performance (!). A way to work around it is using the "sync" mount option, but it comes with a performance penalty in the form of latency from waiting for disk writes to fully complete. Other options include using ZFS, or finding other ways to minimize writes.

Thank you very much. My servers don’t need to be particularly fast, as they will primarily be used for DNS, DHCP, an intranet web server, and shared file backups. Therefore, I believe enabling the "sync" mount option should work well for my needs.

Honestly, you only have the ZFS port (which I don't know the state, stability and completeness, people said it hasn't evolved much since NetBSD 9). WAPBL has proven not to be reliable/fully implemented (after reading tons of mailing lists about that) FFS2 without WAPBL is not journaled so yes there is a risk and I already experienced this to test it with a USB key snatched off without unmounting: There is data loss. Actually NetBSD does not even handle recovery when a volume is uncleanly removed (ripped of) without unmounting. So removing completely the USB without unmounting literally caused the system to hang. I made a post about that a few months back. I know about these because I was trying to reproduce https://unixdigest.com/articles/battle-testing-php-fopen-sqlite-postgresql-and-mariadb-on-ffs-ufs-ext-xfs-and-zfs.html on NetBSD and used a USB drive for that purpose.. WAPBL was not useful at all on that side. Honestly, just do recurrent incremental backups. (and/or ZFS/lvm snapshots)

I should've read about it before I recommended it. After reading [this](https://wiki.netbsd.org/zfs/) I'd say it isn't suitable for your purposes.

NetBSD File system

pfr

Someone correct me if I'm wrong, but wouldn't FreeBSD make more sense for this kind of application? For insight to this comment, I just watched Stefano's EuroBSDCon talk and he talks about running servers that could be at risk of power outage and highlighted FreeBSD as a good choice in this instance.

nia

naguam WAPBL is successful in accomplishing its goals: speed up fsck and improve performance. The result is about the same as other alternatives (e.g. soft updates) for FFS.

htorrado

Having a fault-tolerant file system is important. Perhaps the best solution for a NetBSD server is to have a UPS that gracefully shuts down the server when it detects a power outage and turns it back on when it comes back on.

kc9udx

In my experience it's difficult getting a UPS that will actually cause an orderly shutdown, and impossible to find one that has the means to turn the server back on when power is clean again. If someone knows otherwise I'd be happy to hear it.

Otherwise, since PFS3 isn't available for NetBSD, you could use ZFS. I've no experience with ZFS but I've heard it is pretty resillient.

htorrado

I read that it's possible to install ZFS on the root partition in NetBSD. Do you have any experience with this? How has it worked for you?

https://wiki.netbsd.org/root_on_zfs/

kc9udx

I should've read about it before I recommended it. After reading this I'd say it isn't suitable for your purposes.

nia

kc9udx Unfortunately this document is both outdated and written by a developer who tends to write very pessemistic documentation.

kc9udx

nia November 2024 is outdated?
Anyway I'll bow out and let those who have experience with zfs speak. When Sun first gave it to me I didn't want any part of it.

htorrado

Are there any plans to port Hammer to NetBSD or to provide native support for root on ZFS? I believe NetBSD would benefit from a journaling system.

haihige

htorrado Are there any plans to port Hammer to NetBSD

Seeing that this project has been around for almost 11 years and HAMMER isn't very popular, I doubt it.

rvp

htorrado Here.