[Sheepdog] issues about reading the source code

MORITA Kazutaka morita.kazutaka at lab.ntt.co.jp
Tue Mar 8 18:32:44 CET 2011

At Thu, 3 Mar 2011 14:26:44 +0800,
jidalyg_8711 wrote:
> I'm reading the source code of the sheepdog project, but thers are many 
> terms that I can't understand.
> for example:
> epoch, obj , vdi, journal.....

Sorry, I really think we need more documents about the internal
implementation of Sheepdog.

 - 'Epoch' means the version number of the node membership.  When we
   format the Sheepdog cluster, the epoch number is 1.  If a new node
   joins to the cluster after that, the epoch number will become 2.

 - Sheepdog stores VM volumes by splitting them into 4 MB chunks.  We
   call the chunks 'object'.

 - 'Vdi' is abbreviation of 'Virtual Disk Image'

 - 'Journal' is used to keep vdi objects (metadata of VM volumes) in
   consistent state even when Sheepdog crashes during write

> Do you have some documents that introduces the sheepdog architecture? 
> I really want to learn the sheepdog code and contribute to it.

The slides I presented at KVM Forum 2010 could help you:




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