Freebsd 8.0 kmem map too small

Freddie Cash fjwcash at
Wed May 5 15:19:34 UTC 2010

On Tue, May 4, 2010 at 11:32 PM, Giulio Ferro <auryn at> wrote:

> Giulio Ferro wrote:
>> Thanks, I'll try these settings.
>> I'll keep you posted.
> Nope, it's happened again... Now I've tried to rise vm.kmem_size to 6G...
> I'm really astounded at how unstable zfs is, it's causing me a lot of
> problem.
> Why isn't it stated in the handbook that zfs isn't up to production yet?

As with everything related to computers, it all depends on your uses.

We've been using FreeBSD+ZFS since it first hit 7.0 with very few problems.
The first month of use required a lot of tuning and testing, though, to find
the correct kmem, arc, etc settings for our workload.  Once we found them,
though, things have been rockstable.

We rsync 120 remote Linux and FreeBSD servers to our 24-drive, 18 TB backup
server, every night.  And then rsync that to another similar server.  And
share out a couple of filesytems via NFS and another couple via Samba.

Expect to spend a week or two to tune ZFS, and to rebuild the pool at least
once to find the optimal vdev layout.  But once that's done, expect it to be

Freddie Cash
fjwcash at

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