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

[Adam Heath <doogie@xxxxxxxxxxxxx>]

On Fri, 15 Apr 2005, Mark Williamson wrote:

> > I think the key issue is that in domain configs, you want to specify the
> > source of the vbd in some high-level name and have the control tools do
> > the necessary to map it to a local device and then export it. This
> > already happens with file: disk paths. We just need something similar
> > for iscsi.
>
> To clarify for anyone who hasn't looked into this code, funky (anything that
> is not "phy:") block devices are handled by Xend calling external programs
> (e.g. scripts) with a particular parameter format.  If you specify a VBD
> source device as "file:/my/file" then the following happens (roughly):
>
> Xend looks in its config for an item called "block-file".  In the default
> config (tools/examples/xend-config.sxp) the value of this item is also
> "block-file", which is the name of the script in /etc/xen/scripts.  It then
> calls this script like this:
>
> /etc/xen/scripts/block-file bind /my/file
>
> The script is required to bind /my/file to a loop device, the name of which it
> outputs (e.g. "/dev/loop0") to stdout.  When the domain is destroyed, Xend
> will call:

Would it not be better to just echo /my/file?

> /etc/xen/scripts/block-file unbind /dev/loop0
>
> Likewise specifying a block device "enbd:servername:ctlport" causes a call to
> "/etc/xen/scripts/block-enbd bind servername ctlport" and a subsequent
> "/etc/xen/scripts/block-enbd unbind /dev/enbd_node".
>
> For iSCSI you'd define a syntax like "iscsi:target:lun", write a script to run
> iscsiadm (if you're using OpeniSCSI) and stick it in the config.  You could
> probably do a similar thing to deal with your SAN devices.
>
> Thoughts anyone?  It'd be very desirable to have more block scripts in the
> distribution.  If anyone comes up with some, I don't think there'd be any
> problem with them going into the -testing tree.

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