Re: HAMMER2 design in progress - 1-2 year time frame

["Sascha Wildner" <saw@xxxxxxxxx>]

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.

Regards,
Sascha

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