DragonFly BSD
DragonFly kernel List (threaded) for 2011-07
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Re: HAMMER2 design in progress - 1-2 year time frame

From: "Sascha Wildner" <saw@xxxxxxxxx>
Date: Wed, 06 Jul 2011 09:14:37 +0200

On Sun, 03 Jul 2011 09:12:43 +0200, Steve O'Hara-Smith <steve@sohara.org> wrote:

On Sat, 2 Jul 2011 23:40:53 -0700 (PDT)
Matthew Dillon <dillon@apollo.backplane.com> wrote:

I'll continue to think about how at least a small number of hardlinks
could be implemented without turning already complex cluster
algorithms into a disaster zone. So far I'm drawing a blank.

There are plenty of filesystems that support hard links around, but hardly any that support multi-master clustering. I would say that hard links are a small price to pay for multi-master clustering.

The question is too how many users will use the multi-master feature vs. how many users will be using it as a generic file system on their single machine. Don't know what the answer is to that one, though.

The issue with hard links is that they are part of POSIX and stuff out in the wild will just use it and expect it to work like on most of the other file systems.

We've already had a case where stuff (gdb it was I think) would configure wrongly because hammer would not update file access times on read (which is specified in POSIX too). If there are issues with the hard links missing, I guess they would be along the same lines.

But I have no idea how big a problem it will be in practice.



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