RE: [Xen-devel] VBD extents

[Eric Tessler <maiden1134@xxxxxxxxx>]

 

So in XEN 2.0 is VBD grow/shrink used?  I searched through the source code and could not find anyone who is generating these messages to blkback.  From my understanding, blkback needs the VBD extent info to generate the I/O requests to the real disk device driver (the physical disk on domain 0).  If indeed these messages will eventually be removed, i take it XEND will need to send a message to blkback identifying the disk device driver it should use for I/O (by supplying it a device ID like with the VBD extents).

 

Eric

Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx> wrote:

> > Can anyone tell me what exactly the VBD extents are used for 
> > in the XEN back-end block device driver? It almost looks 
> > like each virtual disk is made up of multiple physical drives 
> > if I read the code correctly (for each VBD grow message 
> > received by blkback, it opens a device and retreives various 
> > info such as its size).
>
> The extent stuff is left over from Xen 1.2, where we effectively had to
> do our own version of LVM inside Xen. We'd like to give the code a
> spring clean and do away with the grow/srink control messages
> altogether. At the same time it would be sensible to add support for
> multiple blk rings, and possibly the ability to 'tunnel' certain ioctls
> e.g. eject CD.
>
> Ian
>
>
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