Re: Disk naming (Was Re: [Xen-devel] [PATCH] Guest boot loadersupport [1/2])

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> > Does that answer your question or am I still off target?
>
> It does.  So, it's the blkback in dom0 that requires a device node.

Yup, that's why we have to go through the gyrations with the block scripts in 
order to make things look nice at the user level.

> How 
> about it the blkback were extended to support files in filesystems?

Right now, all the backend needs to know about is what block device to plumb 
requests through to.  I don't really think there's a nice way to make it 
aware of files within filesystems without effectively reimplementing the 
loopback driver.

From what I've heard the loop driver itself could use a bit of work to make it 
really useful: it comes at a performance / memory usage hit :-(.  We 
recommend using LVM for any really serious environments for this reason.

An alternative architecture would be to have a userspace daemon for file 
backed VBDs, using the blktap framework (unstable tree only).  I'm not sure 
if this would work any better than the current way of doing files, tho...

Cheers,
Mark

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