Re: [Xen-devel] Virtual File System in XEN

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Sep 22, 2011 at 03:31:04PM +0530, Nupur Ghatnekar wrote:
> We are an undergraduate group of students. For our final year project, we
> are planning to implement a Virtual File System in XEN.
> 
> 
> In a paravirtualised environment, an Userspace Application makes a system
> call for access to a file, the domUâs kernel traps it and converts it to an
> appropriate block number. Now this block number is on the Virtual Hard Disk.
> The blktap mechanism is used for block I/O. It involves using XenBus and a

The blktap is deprecated for the upstream kernel - so it won't help you much.

You might be better of using the QEMU backends, like qcow or such.

> daemon in user space of Dom0 which with help of libaio fires the request on
> Dom0 File System. The current scenario involves multiple translations for
> getting the actual physical address.
> 
> 
> Our project intends to reduce the number of translations required during the
> fetching or satisfying of the request.
> 
> The DomU kernel doesnât convert the FS request to block and passes on this
> to dom0 using a client-server mechanism.
> 
> 
> We intend to implement it using the 9P protocol.\
> 
> 1) The domU kernelâs filesystem component will be a client and the dom0 will
> be the server.
> 
> 2) The domUâs kernel will send the file request to dom0 using the 9P
> protocol rather than converting it to appropriate block no.
> 
> 3) The server in dom0 will authenticate the request, process it and send the
> appropriate replies.
> 
> 
> By having a virtual file system, the hypervisor will have a better
> understanding of what the guest domains are doing and hence this can help in
> taking intelligent decisions and thereby have better results in caching,
> de-duplication and snapshots.
> 
> Any suggestions for our proposed project would be appreciated.
> -- 
> 
> Nupur Ghatnekar

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