Re: [Xen-devel] [OSSTEST Nested PATCH v11 5/7] Add new script to customize nested test configuration

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Fri, 2015-06-12 at 03:46 +0000, Pang, LongtaoX wrote:
> 
> > -----Original Message-----
> > From: Ian Jackson [mailto:Ian.Jackson@xxxxxxxxxxxxx]
> > Sent: Thursday, June 11, 2015 11:15 PM
> > To: Pang, LongtaoX
> > Cc: xen-devel@xxxxxxxxxxxxx; Ian.Campbell@xxxxxxxxxx; wei.liu2@xxxxxxxxxx; 
> > Hu,
> > Robert
> > Subject: RE: [OSSTEST Nested PATCH v11 5/7] Add new script to customize 
> > nested
> > test configuration
> > 
> > Pang, LongtaoX writes ("RE: [OSSTEST Nested PATCH v11 5/7] Add new script to
> > customize nested test configuration"):
> > > [Ian Jackson [mailto:Ian.Jackson@xxxxxxxxxxxxx]]
> > 
> > > > We would avoid having to mention /dev/xvdb if we created the VG in the
> > > > host, before doing block-attach.  I'm not sure whether that's an
> > > > improvement.
> > >
> > > I am sorry, I cannot get your point. Could you please make it more
> > > clear? Thanks.
> > 
> > As you explain in the comment, you have to mention /dev/xvdb here even
> > though after rebooting into Xen this will be /dev/sdb.
> > 
> > This wrinkle would become invisible if you did pvcreate and vgcreate
> > in the L0 (before attach), rather than the L1 (after attach).
> > Because, then none of your operations on L1 would not need to name the
> > physical device.
> > 
> Thanks for your explanation.
> For nested job, we will install L2 guest inside L1 reuse 
> 'ts-debian-hvm-install' script.
> But according to recent code design, inside L1 HVM guest, there is no vg 
> group, so that we need to
> create a vg group for L2 installation.
> So, inside L0, we create storage lv(lvcreate -L ${guest_storage_lv_size}M -n 
> $guest_storage_lv_name $vgname), 
> attach this lv to L1. Then inside L1, using the attached disk to create a 
> pv(pvcreate /dev/xvdb),
> then create a vg(vgcreate ${l1_gn}-disk /dev/xvdb) base on the pv. Then, 
> using this vg for installing L2.
> I think '/dev/xvdb' is necessary when create vg inside L1, using command 
> 'vgcreate ${l1_gn}-disk /dev/xvdb' .
> Please correct me if I am wrong.

I think Ian J's suggestion is that instead of creating the ${l1_gn}-disk
VG via commands on /dev/xvdb in the L1 you can create it via commands on
${guest_storage_lvdev} in L0.

e.g. instead of
+target_cmd_root($l1, "pvcreate /dev/xvdb && vgcreate ${l1_gn}-disk /dev/xvdb");
you can instead do:
+target_cmd_root($l0, "pvcreate  ${guest_storage_lvdev} && vgcreate 
${l1_gn}-disk /dev/xvdb");
before you do the block-attach.

That way the VG is already present on the device when it appears in L1
and L1 will just find it.

This avoids any confusion about sdb vs xvdb naming.

Ian.


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