

A quick review of btrfs - rcfox
http://apenwarr.ca/log/?m=201011#11

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pixelbeat
The standard cp since coreutils 7.6 supports the --reflink option. This e.g.
will copy a file with CoW if possible, but fallback to a standard copy if not:

    
    
      cp --reflink=auto src dst
    

I did a quick summary of how reflinks relate to symlinks and hardlinks at
<http://www.pixelbeat.org/docs/unix_links.html>

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kia
The funny thing is that BTRFS is developed by Oracle. ZFS was developed by
Sun. Now when Oracle bought Sun they have two more or less competing
filesystems. What are they going to do about this? Are they going to make ZFS
GPL or cancel the development of one of these?

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rbranson
I doubt they'll make ZFS GPL. ZFS is a really big reason to use Solaris, and
unless they plan on killing Solaris, Linux's paws need to remain off of ZFS.
On the other side of things, Oracle has a LOT of Linux installations, and the
features of ZFS that btrfs is bringing on board are unbelievably useful,
especially in a database environment.

With btrfs, periodic snapshots can be done without touching or "notifying" the
database, in O(1) time. I know that I've setup a PostgreSQL box on ZFS to do
snapshots every 5 minutes, just because it's so "free." Most database software
has some sort of built-in mechanism to do snapshot backups, but they're
generally quite expensive, especially when compared to snapshots in a COW
filesystem like ZFS or btrfs.

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StavrosK
What you're saying is "They won't make ZFS GPL because they want to keep
people on Solaris, but they'll develop btrfs because they want to use it on
Linux".

When the two FSes are so similar, what's the point of developing them both?
They either want the features on Linux, so they should GPL ZFS, or they don't,
and they should discontinue btrfs. Either way, btrfs loses, but either way, we
win (btrfs won't stop being developed, so we'll get a great FS one way or the
other).

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rbranson
Yes, that's exactly what I'm saying. If they GPL ZFS, they end up risking a
major reason people choose Solaris. ZFS is very much a "brand" among systems
administrators. It took quite a while for Sun to convince people to put their
precious business critical data on ZFS, and it'll be the same story for btrfs.

Both of these projects are costing them so little, it's much easier to justify
keeping them going than it is to take on the unknown business risk of making
ZFS directly merge-able into the Linux kernel. Sun clearly chose the CDDL to
keep this from happening, and post-merger, you've probably got the same people
in charge of the Solaris and ZFS projects, so strategies aren't going to
change overnight.

tl;dr: Oracle has low, predictable expenses for development of both btrfs and
ZFS, and there's no reason to rock the boat for <1m/year in expenses.

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danudey
> Yes, that's exactly what I'm saying. If they GPL ZFS, they end up risking a
> major reason people choose Solaris.

Or FreeBSD: <http://www.freebsd.org/doc/handbook/filesystems-zfs.html>

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masklinn
Why would Oracle, of all people, care about FreeBSD?

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apgwoz
> all I know is it's not in the 2.3.36 Linux kernel, but btrfs is, so btrfs
> wins.

I've been out of the Linux kernel loop for ages now, but isn't 2.3.36 over 10
years old? Did they change the naming convention such that development kernels
are 2.3 again? If so, why? Or, am I completely missing something?

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pmjordan
Must be a typo for 2.6.36.

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apgwoz
I assumed that too, but questioned it anyway.

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JshWright
You assumed that... yet in your list of possible reasons, a simple typo wasn't
listed?

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apgwoz
Listing that as a reason would result in multiple people agreeing that it was
a typo and nothing more. If it wasn't a typo, it'd have been overlooked.

