Re: ZFS on rpi3

[Niels Dettenbach <nd%syndicat.com@localhost>]

> Am 22.02.2020 um 15:12 schrieb Sad Clouds <cryintothebluesky%gmail.com@localhost>:
> 
> I'm trying out NetBSD-9 with ZFS on raspberry pi 3. I have 128GB USB SD
> card which has ZFS setup. Noticed that sometimes when under heavy use
> something goes wrong and pgdaemon spins on CPU 100% all the time.
> 
> Not sure if this is something to do with small amount of RAM on this
> machine. Are there any tunables like in FreeBSD
> 
> vm.kmem_size="330M"
> vm.kmem_size_max="330M"
> vfs.zfs.arc_max="40M"
> vfs.zfs.vdev.cache.size="5M"
> 
> that make ZFS play nice when low on RAM?

ZFS is developed with RAM >= 1GB in mind and ZFS is widest tested used on larger systems with significant more RAM as “spindles“ / discs where it can play out it‘s best / features.

And ZFS „performance/ efficiency“ by design strong rely on ARC mem / caches.

So i would assume the huge CPU spikes may be result of a bottleneck in your setup regarding RAM (untypical low arc or even vdev cache).

but this without any deeper insight so far...

Ive found another problem of ZFS (at least FreeBSD) on USB sticks, because some of them seems „incompatible“ so that they „break“ the zfs / leave it inconsistent after some usage (hours / days / weeks) or even „bricked“ USB flash mem. After changing that to a real SSD that problem not happened again.


niels.

—
Niels Dettenbach
https://www.syndicat.com
https://www.syndicat.com/pub_key.asc