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Date:      Wed, 09 Dec 2015 23:26:57 +0100
From:      Michelle Sullivan <michelle@sorbs.net>
To:        Jan Bramkamp <crest@rlwinm.de>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: Periodic jobs triggering panics in 10.1 and 10.2
Message-ID:  <5668AAB1.1080003@sorbs.net>
In-Reply-To: <56683FC1.3050001@rlwinm.de>
References:  <34FA7D40-8758-460D-AC14-20B21D2E3F8D@ebureau.com> <1449619470.31831.9.camel@michaeleichorn.com> <56682278.4040302@sorbs.net> <56683FC1.3050001@rlwinm.de>

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Jan Bramkamp wrote:
> On 09/12/15 13:45, Michelle Sullivan wrote:
>>
>> No that will just hide it (if successful at all) and it won't work in
>> all cases.
>>
>> ... i386 is even worse for similar (not the same) instability triggered
>> by the same scripts ... because zfs should not be used with the stock
>> i386 kernel (which means if you're using it the whole patching process
>> with freebsd-update won't work or will 'undo' your kernel config.)
>
> Do you have a good idea how to prevent users from shooting themselves
> in the foot by running ZFS on 32 Bit kernels?

Yes default not to having zfs available on any platform and allow people
that know what they are doing to turn it on....  I mean "prevent users
from shooting themselves in the foot" - how about by not having an
option to install a zfs root on the default install disks?

>
>> Personally I think zfs should be optional only for 'advanced' users and
>> come with a whole host of warnings about what it is not suitable for....
>> however, it seems to be treated as a magic bullet for data corruption
>> issues yet all I have seen is an ever growing list of where it causes
>> problems.. when did UFS become an unreliable FS that is susceptible to
>> chronic data corruption?
>
> As storage capacity grew a lot faster than reliability.

Yeah, that's why we have these multi-tes-of-terrabyte laptops that must
have a zfs root install...

>
> UFS is a good file system for its time, but it trusts hardware
> absolutely. Modern hardware doesn't deserve this level of trust.

Ok at this point we have to question things...

Does your average home machine need zfs?  (because windows doesn't) ...
does your average laptop require zfs (or even benefit) ...?   In fact
when I look at it, I'm running  70+ servers and a few desktops and I'm
running 5 of them with zfs...  2 of them absolutely need it, 2 of them
are solaris (which probably doesn't count and certainly doesn't have
relevance to FreeBSD) the other is a 2005 P4 based server that is
completely unusable because zfs on i386 doesn't work with the stock
kernel....  and guess what ... it has 73G 15k SCSI Server drives in it
so it probably has reliable hardware that doesn't suffer from "Modern
hardware doesn't deserve this level of trust"

> ZFS detects and recovers without dataloss from most errors caused by
> the limited hardware reliability.

Currently I've had more problems with the reliability of zfs in FreeBSD
than reliability of hardware..  I do get your point though...

>
> ZFS isn't just a tool to deal with hardware limitations it's also a
> convenience I no longer want to give up. Snapshots and replication
> streams simplify backups and a background scrub once a week (or month)
> sure beats waiting for fsck.
Now this is the one set of reasons I can really appreciate and had it
been the opening argument I'd have understood your position, but it
seems this is a side note to the above and the above is where I see it's
completely useless...  When ZFS was first developed a friend and I in
Sun had lots of fun setting up servers where we just chucked any old
drives we could lay our hands on into a pool ... this we found very cool
and this was where 'unreliable' hardware was an understatement - the
drives were pulled from machines because SMART (and other tools) were
reporting the drive(s) failing..... but it was a work around for bad
sectors etc...

Seriously though the default to install with zfs and root on zfs is a
really bad idea - the people who know how not to shoot themselves in the
foot are those people that don't need a selectable option in the install
because they know how to configure it... they're the people who will
probably be in every manual and advanced option they can find anyhow (or
just using boot servers and predefined install scripts)....!!

Regards,

-- 
Michelle Sullivan
http://www.mhix.org/




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