slow ZFS on FreeBSD 8.1

Steven Hartland killing at
Sun Jan 2 16:59:19 UTC 2011

----- Original Message ----- 
From: "Jeremy Chadwick" <freebsd at>
>> Based on my experiences at home, I converted my desktop at work to
>> pure ZFS.  The only issues I've run into have been programs that
>> extensively use mmap(2) - which is a known issue with ZFS.
> Is your ZFS root filesystem associated with a pool that's mirrored or
> using raidzX?  What about mismatched /boot content (ZFS vs. UFS)?  What
> about booting into single-user mode?
> indirectly hints at these problems but
> doesn't outright admit them (yet should), so I'm curious to know how
> people have solved them.  Remembering manual "one-offs" for a system
> configured this way is not acceptable (read: highly prone to
> error/mistake).  Is it worth the risk?  Most administrators don't have
> the tolerance for stuff like that in the middle of a system upgrade or
> what not; they should be able to follow exactly what's in the handbook,
> to a tee.
> There's a link to at the bottom of the above Wiki page
> that outlines "the madness" that's required to configure the setup, all
> of which has to be done by hand.  I don't know many administrators who
> are going to tolerate this when deploying numerous machines, especially
> when compounded by the complexities mentioned above.
With regards installing machines with a root zfs we now use mfsBSD which
makes the process as simple as pie, so for those that haven't used it
give it a wirl:-

> The mmap(2) and sendfile(2) complexities will bite an junior or
> mid-level SA in the butt too -- they won't know why software starts
> failing or behaving oddly (FreeBSD ftpd is a good example).  It just so
> happens that Apache, out-of-the-box, comes with mmap and sendfile use
> disabled.

This is the same with nginx which is rapidly taking over from apache due
to its ability to scale much much better than apache does.

Proper mmap and sendfile integration are the only major issue we have
with moving all our machines to ZFS thanks to great work by everyone.

I really hope sendfile support in particular is fixed in the near future
but as I understanding it, that's not going to be simple at all :(


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