Messages in this thread | | | Date | Fri, 3 Apr 2009 01:00:39 +0100 | From | Matthew Garrett <> | Subject | Re: Ext4 and the "30 second window of death" |
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On Thu, Apr 02, 2009 at 07:38:06PM -0400, Theodore Tso wrote:
> What's been frustrating about this whole controversy is this implicit > assumptions that users and applications should never change, and the > filesystem should magically accomodate and Do The Right Thing.
This is the attitude that I have a significant problem with. Filesystems exist to serve applications. Without applications, there's no reason to have a filesystem. If a filesystem doesn't provide the behaviour that applications want then that filesystem has no reason to exist. The aim isn't to produce a platonically ideal filesystem. The aim is to produce a filesystem that behaves well given the applications that use it.
Disagreeing with the behaviour of applications is a perfectly sensible thing to do. However, it's something that should be done at the *start* of a filesystem development cycle. Getting agreement from a broad section of application developers means that you get to write a filesystem that embodies a different set of assumptions and everyone wins. Writing a filesystem and then bitching about application behaviour after it's been merged to mainline is just pathological.
> The problem is, this is what the application programmers are telling > the filesystem developers. They refuse to change their programs; and > the features they want are sometimes mutually contradictory, or at > least result in a overconstrained problem --- and then they throw the > whole mess at the filesystem developers' feet and say, "you fix it!"
Which application developers did you speak to? Because, frankly, the majority of the ones I know felt that ext3 embodied the pony that they'd always dreamed of as a five year old. Stephen gave them that pony almost a decade ago and now you're trying to take it to the glue factory. I remember almost crying at that bit on Animal Farm, so I'm really not surprised that you're getting pushback here.
> I'm not saying the filesystems are blameless, but give us a little > slack, guys; we NEED some help from the application developers here.
Then having a discussion with application developers over the expectations they can have would be a good first step. Just pointing at POSIX isn't good enough - POSIX allows a bunch of behaviours sufficiently pathological that a filesystem implementing them would be less useful than /dev/null. We need to have a worthwhile conversation about what guarantees Linux will provide above and beyond POSIX. The filesystem summit next week isn't going to be that conversation. Perhaps something to try at Plumbers?
-- Matthew Garrett | mjg59@srcf.ucam.org
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