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Date:      Thu, 10 Dec 2015 09:45:55 -0500
From:      "Michael B. Eichorn" <ike@michaeleichorn.com>
To:        Michelle Sullivan <michelle@sorbs.net>
Cc:        Jan Bramkamp <crest@rlwinm.de>, freebsd-stable@freebsd.org
Subject:   Re: Periodic jobs triggering panics in 10.1 and 10.2
Message-ID:  <1449758755.31831.80.camel@michaeleichorn.com>
In-Reply-To: <56697B32.7050705@sorbs.net>
References:  <34FA7D40-8758-460D-AC14-20B21D2E3F8D@ebureau.com> <1449619470.31831.9.camel@michaeleichorn.com> <56682278.4040302@sorbs.net> <56683FC1.3050001@rlwinm.de> <5668AAB1.1080003@sorbs.net> <1449703798.4355.27.camel@michaeleichorn.com> <56697B32.7050705@sorbs.net>

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On Thu, 2015-12-10 at 14:16 +0100, Michelle Sullivan wrote:
> Michael B. Eichorn wrote:
> > 
> > I sorry, but I really don't get your point, PCBSD has shown a great
> > reason why zfs on root and on laptops/desktops is a good idea...
> > boot
> >   
> 
> It has?  As this is FreeBSD not PCBSD I must have missed that one...

PCBSD is effectively a 'distribution' of FreeBSD, It is just a
different set of defaults and packages with different options. I mean
you can make a FreeBSD install PCBSD by swapping out th repo. I think
using them as an example is within reason.

> > environments. They have pretty much figured out how to use
> > snapshots to
> > go from A-B ping-pong installations to A-B-C-D-E.... installations.
> > I
> > am even aware of people using it to run Release and Current on the
> > same
> > machine. Unfortunately at the moment the system requires GRUB, but
> > there is ongoing work to add the ability to the FreeBSD bootloader.
> >   
> 
> But it's not there yet... and would you consider this for someone who
> is
> not that technical?  (Not that technical != non technical)

I will concede that until the bootloader work is done I would not
recommend boot environments to a less technical user.

> > Further IIRC zfs send-receive has a history involving a developer
> > who
> > wanted a better rsync for transfering his work to a laptop.
> 
> As I said previously these are the features are the ones you listed
> as
> 'additional' (ie your after thoughts)

It wasn't me in the previous email, but if there is any marginal
benifit over UFS for a laptop/desktop it is probably send-receive.

> 
> 
> >  In addition
> > we have pretty much Moore's Lawed our way to the point where a new
> > laptop today can out spec a typical server from when ZFS was first
> > implemented.
> >   
> 
> I have yet to see a 6 spindle laptop...  in fact I've yet to see a 3+
> spindle laptop...

Your are correct here, I was mostly tring to point out the CPU and RAM
on client machines are now up to what servers were at. That said, I
have been running mirrored SSDs since it became an option.

> I could be recalling wrongly but I'm pretty sure a number of emails
> have
> been seen on @freebsd.org lists that say, "don't use zfs on single
> spindle machines"..  what I do know is that personally I have a
> machine
> with a hardware RAID and 16 drives...  Initially I configured it with
> 1
> large LD RAID6+HSP and put zfs on it (because I wanted to take
> advantage
> of the 'on the fly compression')... it's a backup store... and every
> scrub checksum errors were found - on files that had not been written
> to
> since the last scrub.  I reconfigured it as 16 x single disk RAID0
> drives - identical hardware, just a different config, put raidz2
> across
> 15 drives and left one as a spare and now I don't have any errors
> except
> when a drive fails and even then it 'self heals'...

Hmm, the advice that ZFS advocates such a Allan Jude have been giving
of late is that ZFS can work in single spindle. It is just that it is
less safe (like any single disk) but is not more data-loss prone than
other forms of striping.

> > Hiding features because you 'can' shoot your foot off is hardly a
> > typical UNIXy way of thinking anyway.
> 
> Not talking about 'hiding' features, even though this thread started
> with someone suggesting 'hiding' a bug by using -J and -j options for
> cron....!

I will fess up, It was me who suggested -J and -j, but it was more in
the sense of improving the work-around (the OP had just stopped running
cron in jails). It was not ment to imply the bug shouldn't be fixed,
all bugs should be fixed and not hidden.

> Look I'm being quite confrontational here in this message, there are
> a
> lot of people that don't like me here, and I don't like some of them
> myself so the feeling is very mutual, the point I'm trying to make is
> quite simple.

I must admit to being a bit 'heated' too, but I kind of like debates
and I take no personal grievance, or have any problem with you. It is a
technical discussion with strongly held beliefs. Further despite the
emotions I applaud the continued use of professional language.

> I see it almost daily, FreeBSD people saying "install ZFS that'll
> solve
> your problems" and "ZFS it's the way forward" ...  just the same way
> as
> they did with PkgNG etc... (not going to say anything on that, don't
> want an argument on that, this is not about 'that'..)
> 
> ZFS has it's place, it is very good at some things, it brings
> features
> that people need.
> ZFS does not work (is not stable) on i386 without recompiling the
> kernel, but it is presented as an installation option.
> ZFS is compiled in by default in i386 kernels without the necessary
> option change to make it "stable".
> We have been told the kernel option change will never be put there by
> default.
> freebsd-update will remove/replace a kernel compiled with the option
> i386 is still a teir1 platform.
> 32bit laptops are still available for purchase at major retailers
> (eg:
> Bestbuy)

You are correct, ZFS is not a panacia, and they clearly have different
use cases. I would never use ZFS for an embedded system, or UFS for a
big-iron fileserver. I think our disagreement is on the laptop/desktop,
I think both technologies are able to handle the laptop/desktop just
fine, so it really comes down to personal preference in what features
are most important. I responded so forcefully previously because I
perceived that you were saying ZFS was the wrong choice for that
workload. I just don't see evidence that for a typical laptop/desktop,
which I take to mean an amd64 machine (probably newer than core2) and
with at least 4GB of RAM, is likly to have a significant problem
running either.

As to i386, I concur running ZFS on them at all is questionable. 386
was outside of the design intent, and it should not be done. I suppose
I was living in my happy place where i368 is slowly being phased out of
the hands of non-expert users. *sigh* Best Buy *shakes head*.

> I do not believe zfs should be default available when it is not
> stable
> on all teir1 platforms.  I believe it should be fixed to be stable
> before its added as an installation option to teir1 platforms and if
> it
> cannot/willnot be fixed to 'stable' status then it should never make
> it
> into the defaults available... it should be limited to be in advanced
> installations where the people who know will probably know how to fix
> things or what to expect.

I think the defaults are going to get even muddier than this, after all
IIRC arm is going to be tier1 in 11. I have heard nothing at all about
ZFS on arm, but even if the processors could handle it most arm boards
don't have much RAM.

In the past where amd64 and i386 were the tier1 supports I could see
some advantage to keeping the defaults more in sync with each other.
However, given how different arm can be perhaps it is time to
reconsider the defaults in i386. I suppose the devs may have a better
reason for ZFS is i386, but _this_ is probably a productive
conversation to have.

> ..anyhow my thoughts on the subject..  why I don't know because in
> the
> time it has taken me to write this, it occurred to me, I don't give a
> stuff really if people see FreeBSD as stable or unstable anymore.  I
> put
> forward experiences and what I see and the questions/answers I have
> to
> deal with here and am usually ignored or argued with and I spend 30
> minutes (or more) writing emails explaining stuff/defending myself to
> people who don't care and think (like me) they know best when I could
> actually be doing the work I get paid for.  On that note I will leave
> you to considerand discard my thoughts as trivial and pointless and
> reply as such and get on with making my stuff better by actually
> listening to people who use it.

Again, I appreciate your points, I think you just came off originally
as very dismissive that ZFS is an option for laptops. I reacted
strongly, as have you, but I take no malice or offense, nor have any
towards yourself. Your arguements have spurred thinking at least on my
part as to what the defaults should be for i386. If anyone is being the
ID10T here, it is probably me anyway.

If I might make a recommendation, I think that a separate thread about
the i386 defaults is probably in order as I imagine the length of these
emails has probably turned most people off.



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