ZFS on RPi (was: zfs on BeagleBone)

[Brett Wynkoop]

On Sat, 21 Mar 2015 17:53:46 +1100
Peter Jeremy <peter at rulingia.com> wrote:


> panic: vm_fault: fault on nofault entry, addr: dd2f1000
> KDB: stack backtrace:
> Uptime: 11m46s
> Physical memory: 473 MB
> Dumping 36 MB:sdhci_bcm0: DMA in use
> 
> The tuning I did was:
> vfs.zfs.arc_max="24M"
> vfs.zfs.vdev.cache.size="5M"
> 

Sorry for the delay.  Other things have kept me from being as attentive
to the arm list as I might like.

It seems you did not tune vm.kmem_size.  In my experience with smallish
systems running FreeBSD with zfs that is mandatory.  My 256M BBone has
this:

vm.kmem_size="256M"

vm.kmem_size_max="256M"

#vfs.zfs.arc_max="40M"
#vfs.zfs.arc_max="64M"
vfs.zfs.arc_max="24M"

vfs.zfs.vdev.cache.size="5M"

I strongly suggest setting vm.kmem_size to your real memory and do the
same with vm.kmem_size_max.  I came up with this after doing loads of
reading for zfs on memory restricted systems.

Remember by default zfs really wants at least 1GB main memory, and that
is still tight, most references claim 2GB is the practical lower limit
on x86.  I have it running on an x86 box with 512MB, but could not make
it run on 384MB on FreeBSD x86.

-Brett

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