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b/doc/design-glusterfs-ganeti-support.rst
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  uses libgfapi and hence there is no FUSE overhead any longer when QEMU/KVM
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  works with VM images on Gluster volumes.
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There are two possible ways to implement "GlusterFS Ganeti Support" inside


  		





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Ganeti. One is based on libgfapi, which call APIs by libgfapi to realize


  		





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GlusterFS interfaces in bdev.py. The other way is based on QEMU/KVM. Since


  		





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QEMU/KVM has supported for GlusterFS and Ganeti could support for GlusterFS


  		





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by QEMU/KVM. However, the latter way can just let VMs of QEMU/KVM use GlusterFS


  		





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backend storage but other VMs like XEN and such. So the first way is more


  		





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suitable for us.


  		





  
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Proposed implementation


  		





  
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-----------------------


  		





  
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QEMU/KVM includes support for GlusterFS and Ganeti could support GlusterFS


  		





  
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through QEMU/KVM. However, this way could just let VMs of QEMU/KVM use GlusterFS


  		





  
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backend storage but not other VMs like XEN and such. There are two parts that need


  		





  
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to be implemented for supporting GlusterFS inside Ganeti so that it can not only


  		





  
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support QEMU/KVM VMs, but also XEN and other VMs. One part is GlusterFS for XEN VM,


  		





  
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which is similar to sharedfile disk template. The other part is GlusterFS for


  		





  
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QEMU/KVM VM, which is supported by the GlusterFS driver for QEMU/KVM. After


  		





  
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``gnt-instance add -t gluster instance.example.com`` command is executed, the added


  		





  
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instance should be checked. If the instance is a XEN VM, it would run the GlusterFS


  		





  
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sharedfile way. However, if the instance is a QEMU/KVM VM, it would run the


  		





  
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QEMU/KVM + GlusterFS way. For the first part (GlusterFS for XEN VMs), sharedfile


  		





  
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disk template would be a good reference. For the second part (GlusterFS for QEMU/KVM


  		





  
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VMs), RBD disk template would be a good reference. The first part would be finished


  		





  
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at first and then the second part would be completed, which is based on the first


  		





  
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part.


  		





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