[Xen-devel] Virtual File System in XEN

[Nupur Ghatnekar <nupurghatnekar@xxxxxxxxx>]

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 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.Â

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.Â

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.
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Nupur Ghatnekar
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