On 6/16/2011 12:09 AM, Simon Walter wrote:
On 06/16/2011 09:09 AM, Erik Trimble wrote:
We had a similar discussion a couple of years ago here, under the
title "A Versioning FS". Look through the archives for the full
discussion.
The jist is that application-level versioning (and consistency) is
completely orthogonal to filesystem-level snapshots and consistency.
IMHO, they should never be mixed together - there are way too many
corner cases and application-specific memes for a filesystem to ever
fully handle file-level versioning and *application*-level data
consistency. Don't mistake one for the other, and, don't try to
*use* one for the other. They're completely different creatures.
I guess that is true of the current FSs available. Though it would be
nice to essentially have a versioning FS in the kernel rather than an
application in userspace. But I regress. I'll use SVN and webdav.
Thanks for the advice everyone.
It's not really a technical problem, it's a knowledge locality problem.
The *knowledge* of where to checkmark, where to version, and what data
consistency means is held at the application level, and can ONLY be
known by each individual application. There's no way a filesystem (or
anything like that) can make the proper decisions without the
application telling it what those decisions should be. So, what would
the point be in having a "smart" versioning FS, since the intelligence
can't be built into the FS, it would still have to be built into each
and every application.
So, if your apps have to be programmed to be
versioning/consistency/checkmarking aware in any case, how would having
a fancy Versioning filesystem be any better than using what we do now?
(i.e. svn/hg/cvs/git on top of ZFS/btrfs/et al) ZFS at least makes
significant practical advances by rolling the logical volume manager
into the filesystem level, but I can't see any such advantage for a
Versioning FS.
--
Erik Trimble
Java Platform Group Infrastructure
Mailstop: usca22-317
Phone: x17195
Santa Clara, CA
Timezone: US/Pacific (UTC-0800)
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