accessing a char device in xenU

accessing a char device in xenU

[Matthieu PATOU]

Hi
is it possible to access a char device in xenU ?
More precisly i have i tape device in a server and i want to share it across
my different xenU domains.

Any clues ?
Matthieu


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Re: accessing a char device in xenU

[Mark Williamson]

> > 'phy:/dev/sdb,sdb,w'
>
> i was talking about a char device (a dat tape).
> So the only solution is to hide the whole card and export it into another
> xenU ...

Ah, sorry.

No, we don't provide virtualisation at the SCSI command layer so you'll have 
to either export the whole PCI card or use a network-based solution.  My 
preference would be for the network-based solution unless you have a really 
strong reason to use PCI exporting.

CHeers,
Mark


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Re: accessing a char device in xenU

[Matthieu]

On February 10, 11:38 pm Mark Williamson <maw48@cl.cam.ac.uk> wrote:
> >  Is it possible to make a scsi device invisible from xen0 and visilbe
> >  in xenU (i'm not talking of a whole scsi card but just one device on
> >  the card) ?
>
> You can't make it invisible in dom0 but you can export it to a domU
> using the standard virtual block device configuration. i.e.:
>
> 'phy:/dev/sdb,sdb,w'
i was talking about a char device (a dat tape).
So the only solution is to hide the whole card and export it into another
xenU ...

matthieu


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Re: accessing a char device in xenU

[Mark Williamson]

> Is it possible to make a scsi device invisible from xen0 and visilbe in
> xenU (i'm not talking of a whole scsi card but just one device on the card)
> ?

You can't make it invisible in dom0 but you can export it to a domU using the 
standard virtual block device configuration. i.e.:

'phy:/dev/sdb,sdb,w'

Cheers,
Mark

> > With a dvice like a tape you'd presumably only want to let one domain
> > access it at a time, perhaps with a hard interlock as to which tape is
> > in the drive. Fortunately, the bandwidth is pretty low, so it's probably
> > easiest to setup a network based soloution rather than doing something
> > Xen specific. I presume such daemons already exist (?)
>
> Sure something like amanda should work ...
>
>
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Re: accessing a char device in xenU

[Matthieu PATOU]

Sorry for my late comment on this email ...
> > Hi
> > is it possible to access a char device in xenU ?
> > More precisly i have i tape device in a server and i want to 
> > share it across
> > my different xenU domains.
> 
> No, there's no generic mechanism for sharing char devices. The way in
> which it makes sense to multiplex devices between domains is typically
> very device-secific:
> 
Is it possible to make a scsi device invisible from xen0 and visilbe in xenU
(i'm not talking of a whole scsi card but just one device on the card) ?

> With a dvice like a tape you'd presumably only want to let one domain
> access it at a time, perhaps with a hard interlock as to which tape is
> in the drive. Fortunately, the bandwidth is pretty low, so it's probably
> easiest to setup a network based soloution rather than doing something
> Xen specific. I presume such daemons already exist (?)
Sure something like amanda should work ...


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RE: accessing a char device in xenU

[Ian Pratt]

> Hi
> is it possible to access a char device in xenU ?
> More precisly i have i tape device in a server and i want to 
> share it across
> my different xenU domains.

No, there's no generic mechanism for sharing char devices. The way in
which it makes sense to multiplex devices between domains is typically
very device-secific:

With a dvice like a tape you'd presumably only want to let one domain
access it at a time, perhaps with a hard interlock as to which tape is
in the drive. Fortunately, the bandwidth is pretty low, so it's probably
easiest to setup a network based soloution rather than doing something
Xen specific. I presume such daemons already exist (?)

Ian



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