Re: slow ZFS on FreeBSD 8.1
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On 2010-Dec-31 15:47:47 -0800, Jeremy Chadwick <freebsd@jdc.parodius.com> w=
rote:
>Is your ZFS root filesystem associated with a pool that's mirrored or
>using raidzX?
Currently, mirrored. I'm considering raidz1 at home. Note that my
work system is a single pool, whereas I'll use a separate pool for
root at home.
> What about mismatched /boot content (ZFS vs. UFS)?
Can you give me an example of what you mean here.
> What about booting into single-user mode?
I haven't run into any problems here, though I agree that starting
ZFS in single-user mode is a lot messier than starting UFS.
>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.
I've been using FreeBSD for long enough that I'm confident to upgrade
or similar without blindly following a process. But I agree that
FreeBSD should be usable without needing to be a guru.
>There's a link to www.dan.me.uk 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.
Root on ZFS is still very bespoke. I agree there's no way you could
roll it out across lots of machines at present but I'm happy to hand-
craft installs on a few machines. Hopefully, son-of-sysinstall will
support ZFS installs (one prerequisite is someone being willing to do
the work).
>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.
mmap(2) is a design problem with ZFS - it's present on Solaris as
well. IMHO, it's the biggest flaw in ZFS. The sendfile(2) issues
haven't bitten me so I haven't studied them as much but I'm aware
that some fixes were committed recently.
Oh and one root-on-ZFS gotcha that I missed is the lack of gzip
support. I spent about =BDday tracking that down - not helped by the
lack of any documentation or a useful error message (though there is a
comment in the code when you eventually track it down).
--=20
Peter Jeremy
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