[haiku-development] Re: ext3 Journal Design Considerations

  • From: Alexander Botero-Lowry <alex.boterolowry@xxxxxxxxx>
  • To: Sean Bartell <wingedtachikoma@xxxxxxxxx>, haiku-development@xxxxxxxxxxxxx
  • Date: Tue, 13 Apr 2010 19:58:31 -0700

On Tue, 13 Apr 2010 22:46:09 -0400, Sean Bartell <wingedtachikoma@xxxxxxxxx> 
wrote:
> On Wed, Apr 14, 2010 at 02:36:51AM +0000, Janito Ferreira Filho wrote:
> > The second 
> > use would also be for future-proofing for external journals. The idea is
> >  to "rename" the Volume class into "Ext3Volume", and have a parent 
> > generic "Volume" containing just basic functions (and a block cache). 
> > This allows me to initiate a Journal with two Volumes, one for the 
> > journal and one for the file system. Somehow I feel that this solution 
> > is somewhat less elegant. What does everyone think? Am I complicating 
> > things too much?
> 
> I think it's worth keeping in mind that, at some point, Haiku will have
> to support filesystems based on multiple volumes (ZFS, Btrfs, maybe
> LVM). Maybe that could be done generically and used to support external
> journals? There would need to be a general way to determine which
> volumes are part of the same filesystem.
> 
It's worth taking a look at FreeBSD's GEOM. It's not specifically a
volume manager but allows for the implementation of them. As well as
pretty much any other IO-layering thing you want to do like
disk-replication, over the network mounting of block devices, disk
encryption, and journaling. All possible in arbitrary arrangements (at
least in theory). 

alex

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