On Wed, Oct 12, 2016 at 6:29 AM, Gerald B. Cox <gb...@bzb.us> wrote:
> On Tue, Oct 11, 2016 at 8:52 PM, Chris Murphy <li...@colorremedies.com>
> wrote:
>> About the rewrite comment: that did not come from a developer, and is
>> definitely overstated. In any case, rewrites are not inherently bad
>> news, there's a bunch of OpenZFS videos from last yearss summit in
>> which the developers talk about various things being completely
>> rewritten from scratch, some things more than twice. So kinda par for
>> the course, and given enough time things get rewritten anyway. XFS has
>> had substantial changes over its history including numerous on disk
>> format changes even before it found its way onto Linux.
> Could be, should be, may be... that's fine - but it all says the same
> thing... they
> don't know how much time it is going to take to fix - and who knows what
> their
> priority is to get around to it.  The advantages over what already is
> available
> don't appear to be that compelling, especially when weighed with the risks.

So you are saying that you started using raid56 when it was brand new,
before it had *any* kind of persistent repairing or device replacement
and only now, due to a bug that manifests remarkably less bad than the
normal behavior of everything else (minus ZFS), are you now
complaining? So basically this is, "I want it now!" complaint. Because
all the available information has been saying don't use raid56 for
production, but you did so anyway. This is a subjective change in your
evaluation. It has nothing to do with the state of Btrfs so you really
shouldn't blame it when your requirements have clearly changed.

> When all this started I did some searches and found Kent Overstreet's page
> on
> bcachefs:  https://goo.gl/U0UFfN
> He had some words about the different filesystems - and had this to say
> about btrfs:
> btrfs, which was supposed to be Linux's next generation COW filesystem -
> Linux's answer to zfs. Unfortunately, too much code was written too quickly
> without focusing on getting the core design correct first, and now it has
> too many design mistakes baked into the on disk format and an enormous,
> messy codebase - bigger that xfs. It's taken far too long to stabilize as
> well - poisoning the well for future filesystems because too many people
> were burned on btrfs, repeatedly (e.g. Fedora's tried to switch to btrfs
> multiple times and had to switch at the last minute, and server vendors who
> years ago hoped to one day roll out btrfs are now quietly migrating to xfs
> instead).

I have heard from a couple developers that it was a victim of its own
hype/success and too many feature additions without equivalent effort
on error reporting, debugging, and fault injection tools. I have yet
to hear a Btrfs developer say the core design or on disk format has
anything to do with the problems, but to the contrary. The comment
it's bigger than XFS is kinda funny, seeing as it does more than XFS,
md, and LVM combined, so a proper comparison would be comparing all of
them to Btrfs minus their user space tools (for sure Btrfs tools do
not come anywhere near the metric ass tonne of switches or
documentation in LVM or mdadm).

The Fedora report is simply nonsense. Fedora made no meaningful
attempt to switch to Btrfs once, let alone multiple times. FESCo
considered and approved it, with conditions attached. Josef kept
pushing it off because he thought it wasn't ready. And then Josef
moved on from Red Hat, and wasn't replaced. Characterizing this as
"tried to switch" and "had to switch at the last minute" is at best
hyperbole. It was a change proposal, and it never met the requirements
of either the proposer or FESCo for it to proceed further. No changes
in default happened in the installer that had to be reverted.

Perhaps the secret of fast and stable fs development is a single
developer authored file system.

Chris Murphy
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