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xen-users
Re: [Xen-users] FC3 domU using Xen 3.0
Thanks everybody. I'll investigate more and keep you updated.
More details on "xvd" devices will be appreciated.
Thanks again,
Andrea
On 1/15/07,
Roger Lucas <roger@xxxxxxxxxxxxx> wrote:
> > >Here's my config file:
> > >
> > >kernel ="/boot/vmlinuz-2.6.18-1.2869.fc6xen"
> > >#ramdisk = "/boot/initrd-2.6.18-1.2869.fc6xenU.img"
> > >memory = 256
> > >name = "mail"
> > >vif = ['mac=aa:00:00:00:00:01']
> > >disk =
> > >['file:/xen/mail/fedora.img,sda1,w','file:/xen/mail/swap1.img,sda2,w']
> >
> > I would not use file-based devices as block devices on production
> > systems. I heard people having a lot trouble with them.
>
> File backed devices are fine provided you:
>
> 1. Use the blktap async-io backend - eg, tap:aio: instead of file:
> 2. Pre-allocate the entire extent of the file - ie do NOT use a
> sparse file - it has unpredictable performance characteristics,
> and is unsafe if the host FS fills up.
>
> > >root = "/dev/sda1"
> > >extra = "ro selinux=0 3"
> > >
> > >This is the error I get:
> > >VFS: Cannot open root device "sda1" or unknown-block(0,0)
> > >Please append a correct "root=" boot option
> > >Kernel panic - not syncing: VFS: Unable to mount root fs on
> > >unknown-block(0,0)
> >
> > Try using xvda, or add the scsi dik driver manually to the fedora
> > Initrd. I think fedora wants to work only with xvda drives in DomU...
>
> Fedora will work with sda/hda devices, however, we strongly recommend
> you do NOT use them because its is practically 100% guarenteed support
> will be removed when Xen guest patches are merged upstream. So to future
> proof yourself only use the 'xvdN' block devices in the guest.
>
> > And, I'm not sure if fedora Xen Package can use the phy: block
> > devices. At least, every domain created with their virt-install tool
> > uses blocktap tap:aio for block device access.
>
> You can use phy: if you're mapping in a physical device from the host.
> The virt-install choose will automatically choose eithe phy: or tap:aio:
> depending on whether the host side is a file or a block device. For
> fully-virt (HVM) guests it will use file: instead of tap:aio: since
> blktap is only meaningful for paravirt at this time.
>
Can you explaina bit more about the "xvd" device type?
I am running Xen-3.0.4 on Ubuntu 6.10 with the Xen binary kernels and if I
use "xvda" rather than "hda", my Ubuntu DomU seems to run as well as if I
used "hda"....
The Xen manual for 3.0.4 on p16 recommends a configuration such as:
disk = ['phy:your hard drive%d,sda1,w' % (base partition number + vmid),
'phy:your usr partition,sda6,r' ]
I have checked the Xen wiki, the PDF manual in the Xen source, "grep"d the
Xen 3.0.4 source as well as googled for "xen xvd". I have found a few
references to "xvd" devices but nothing that explains why it exists or why
you should use it instead of "sda" or "hda"....
Can you offer any insight as to when/if xvda should be used instead of hda
or sda?
Thanks,
Roger
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