HAMMER2 design in progress - 1-2 year time frame

Sascha Wildner saw at online.de
Wed Jul 6 00:14:37 PDT 2011

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

On Sat, 2 Jul 2011 23:40:53 -0700 (PDT)
Matthew Dillon <dillon at apollo.backplane.com> wrote:
    I'll continue to think about how at least a small number of  
    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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