[Qemu-devel] Re: Release: USB image of OS Circular and deb packages of LBCAS (LoopBack Content Addressable Storage)

[Kuniyasu Suzaki]

Hello Alex,

 >>From: Alexander Graf <address@hidden>
 >>Subject: Re: Release: USB image of OS Circular and deb packages of LBCAS 
 >>(LoopBack Content Addressable Storage)
 >>
 >>Kuniyasu Suzaki wrote:
 >>> Hello,
 >>>
 >>> We released bootable USB image of "OS circular" and the Debian packages of 
 >>> LBCAS (LoopBack Content Addressable Storage).
 >>
 >>Looking at the backend (LBCAS) that is the actually interesting part: Is
 >>there any reason you implemented this as FUSE plugin?

Because it is easy to implement a virtual loopback file.
A real content, which is save to a block-file, is mapped to the
virtual loopback file when a block is accessed.  The mapping is a kind
of indirect addressing, which translates physical address to
block-file name (SHA1 digest of its contents). The management is
achieved by FUSE.

 >>I was thinking of implementing something like this myself for SUSE
 >>Studio and figured the best way to do it would be to make it a qemu
 >>block driver backend, en par with the "posix-raw" one. That way you
 >>wouldn't need FUSE to download images on demand and also enable this
 >>features for say Windows users.

Good idea.
OS Circular, however, is designed to be applied to any virtual
machines, i.e., VirtualBox, VMWare, etc. OS Circular also aims to
applied to REAL MACHINE.
Please refer the big picture of OS Circular project.
   http://openlab.jp/oscircular/big-picture.PNG

 >>So is there any plan on your side to write something like this for
 >>upstream Qemu? If not that's fine too, I just need to know if I'd have
 >>to do it myself :-).

Please make your backend driver :-).
I want to ask you to fix the blocking I/O of loopback device.
It would be another topic discussed in this ML threads.

------
suzaki