Re: Virtualization project idea

["Pasi Kärkkäinen" <pasik@iki.fi>]

On Fri, Aug 27, 2010 at 04:56:33PM +0530, Dhananjay Goel wrote:
>    Also you wouldn't see the changes made in other VMs,
>    unless you made sure all the caches are refreshed etc in the VM all the
>    time.
> 
>    You'd need to use some cluster-filesystem (GFS, GFS2, OCFS2, GPFS, etc).
>    --Can you please suggest how NFS manages this because this case is handled
>    by NFS without any corruption?
>    We can share flash drive across VMs as we do with physical machines in
>    LAN. Please help!
> 

How are you sharing USB flash drives with physical machines? 

-- Pasi

>    Thanks,
>    Dhananjay
> 
>    On Fri, Aug 27, 2010 at 4:27 PM, Pasi Kärkkäinen <[1]pasik@iki.fi> wrote:
> 
>      On Fri, Aug 27, 2010 at 02:53:54PM +0530, Dhananjay Goel wrote:
>      >    This won't be straight forward. Think about USB memory/flash stick.
>      >    If every VM sees it, and simultaneously writes to it, the
>      filesystem
>      >    in it will get corrupted immediately!
>      >
>      >    --Why would it get corrupted immediately. Might be we can just lock
>      a
>      >    specific file which is being edited? Please suggest.
>      >
> 
>      Because USB level has no idea about filesystems or files, or locking
>      them!
> 
>      Say you're using ext3 or NTFS in the VM for the USB device.
>      Those filesystems are NOT cluster-aware, ie. they're not aware of any
>      sharing,
>      and they don't support any kind of sharing.
> 
>      They expect exclusive access to the device.
> 
>      If suddenly the bits on the device change from outside,
>      the filesystem gets corrupted very easily.
> 
>      Also you wouldn't see the changes made in other VMs,
>      unless you made sure all the caches are refreshed etc in the VM all the
>      time.
> 
>      You'd need to use some cluster-filesystem (GFS, GFS2, OCFS2, GPFS, etc).
> 
>      -- Pasi
> 
>      >    Thanks,
>      >    Dhananjay
>      >
>      >    On Fri, Aug 27, 2010 at 2:49 PM, Pasi Kärkkäinen
>      <[1][2]pasik@iki.fi> wrote:
>      >
>      >      On Fri, Aug 27, 2010 at 02:45:12PM +0530, Dhananjay Goel wrote:
>      >      >    No, that's not possible with pvusb. pvusb is for direct
>      passthru to
>      >      >    one/single vm.
>      >      >    You'd need some filesystem share (cifs/nfs/whatnot) to make
>      such
>      >      sharing
>      >      >    possible.
>      >      >    Comments: Is it possible to share USB keyboard, USB mouse,
>      USB
>      >      modem, etc
>      >      >    across VMs i.e host and guest(s)? If we connect USB
>      keyboard, is it
>      >      >    possible to use it in guests?
>      >      >
>      >
>      >      This is implemented in XCI (Xen Client Initiative), and there has
>      been
>      >      some discussions how to get it traditional Xen, to help Xen VGA
>      >      Passthrough usage.
>      >
>      >      See: [2][3]http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>      >      >    Also, is it possible for us to modify the device driver of
>      USB 2.0
>      >      so that
>      >      >    all USB 2.0 devices are visible and can be used across all
>      VMs?
>      >      Please
>      >      >    suggest.
>      >      >
>      >
>      >      This won't be straight forward. Think about USB memory/flash
>      stick.
>      >      If every VM sees it, and simultaneously writes to it, the
>      filesystem
>      >      in it will get corrupted immediately!
>      >
>      >      USB Passthru cannot be used to 'share' devices, it's for giving
>      >      one/single VM
>      >      direct access to the device.
>      >
>      >      -- Pasi
>      >
>      >      >    Thanks,
>      >      >    Dhananjay
>      >      >
>      >      >    On Fri, Aug 27, 2010 at 2:16 PM, Pasi Kärkkäinen
>      >      <[1][3][4]pasik@iki.fi> wrote:
>      >      >
>      >      >      On Fri, Aug 27, 2010 at 01:37:49PM +0530, Dhananjay Goel
>      wrote:
>      >      >      >    Hi James/Pasi,
>      >      >      >    I had a look at
>      >      >
>       [1][2][4][5]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >      >      >    But I'm not sure if it supports sharing USB devices
>      across
>      >      VMs
>      >      >      (host and
>      >      >      >    guest) i.e. if I plug in a flash drive then it would
>      detect
>      >      in both
>      >      >      host
>      >      >      >    and guest and I'd be able edit files from all VMs
>      rather
>      >      than
>      >      >      mounting and
>      >      >      >    unmounting everytime from 1 VM to other.
>      >      >      >    Please let me know your thoughts on it.
>      >      >      >
>      >      >
>      >      >      No, that's not possible with pvusb. pvusb is for direct
>      passthru
>      >      to
>      >      >      one/single vm.
>      >      >      You'd need some filesystem share (cifs/nfs/whatnot) to
>      make such
>      >      sharing
>      >      >      possible.
>      >      >
>      >      >      -- Pasi
>      >      >      >    Thanks,
>      >      >      >    Dhananjay
>      >      >      >
>      >      >      >    On Fri, Aug 27, 2010 at 4:28 AM, James Harper
>      >      >      >    <[2][3][5][6]james.harper@bendigoit.com.au> wrote:
>      >      >      >
>      >      >      >      > Hi there!
>      >      >      >      >
>      >      >      >      > First I'd like to say that XEN plaform is really
>      cool
>      >      and
>      >      >      awesome.
>      >      >      >      >
>      >      >      >      > I'm an engineering student and is searching for a
>      >      feasible
>      >      >      project in
>      >      >      >      > virtualization. I'd like to know if its possible
>      to
>      >      share USB
>      >      >      devices
>      >      >      >      (flash
>      >      >      >      > drive, hard disk, mouse, keyboards etc) across
>      guests
>      >      and host
>      >      >      (VMs).
>      >      >      >      Also, do
>      >      >      >      > you have any idea to extend it? Or any innovative
>      idea
>      >      so that
>      >      >      we can
>      >      >      >      > implement it.
>      >      >      >      >
>      >      >      >      > I'd appreciate any help. Thanks in advance.
>      >      >      >      >
>      >      >      >
>      >      >      >      Further to what Pasi said, I have partially ported
>      the
>      >      backend
>      >      >      interface
>      >      >      >      and can hand you the code if you want. It's
>      probable a bit
>      >      stale
>      >      >      vs the
>      >      >      >      current kernels and leaks memory under some
>      circumstances
>      >      but is
>      >      >      >      probably better than starting from scratch.
>      >      >      >      James
>      >      >      >
>      >      >      > References
>      >      >      >
>      >      >      >    Visible links
>      >      >      >    1.
>      [4][6][7]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >      >      >    2. mailto:[5][7][8]james.harper@bendigoit.com.au
>      >      >
>      >      > References
>      >      >
>      >      >    Visible links
>      >      >    1. mailto:[8][9]pasik@iki.fi
>      >      >    2.
>      [9][10]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >      >    3. mailto:[10][11]james.harper@bendigoit.com.au
>      >      >    4.
>      [11][12]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >      >    5. mailto:[12][13]james.harper@bendigoit.com.au
>      >
>      > References
>      >
>      >    Visible links
>      >    1. mailto:[14]pasik@iki.fi
>      >    2. [15]http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>      >    3. mailto:[16]pasik@iki.fi
>      >    4. [17]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >    5. mailto:[18]james.harper@bendigoit.com.au
>      >    6. [19]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >    7. mailto:[20]james.harper@bendigoit.com.au
>      >    8. mailto:[21]pasik@iki.fi
>      >    9. [22]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >   10. mailto:[23]james.harper@bendigoit.com.au
>      >   11. [24]http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>      >   12. mailto:[25]james.harper@bendigoit.com.au
> 
> References
> 
>    Visible links
>    1. mailto:pasik@iki.fi
>    2. mailto:pasik@iki.fi
>    3. http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>    4. mailto:pasik@iki.fi
>    5. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>    6. mailto:james.harper@bendigoit.com.au
>    7. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>    8. mailto:james.harper@bendigoit.com.au
>    9. mailto:pasik@iki.fi
>   10. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   11. mailto:james.harper@bendigoit.com.au
>   12. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   13. mailto:james.harper@bendigoit.com.au
>   14. mailto:pasik@iki.fi
>   15. http://wiki.xensource.com/xenwiki/XenVGAPassthrough
>   16. mailto:pasik@iki.fi
>   17. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   18. mailto:james.harper@bendigoit.com.au
>   19. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   20. mailto:james.harper@bendigoit.com.au
>   21. mailto:pasik@iki.fi
>   22. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   23. mailto:james.harper@bendigoit.com.au
>   24. http://wiki.xensource.com/xenwiki/XenUSBPassthrough
>   25. mailto:james.harper@bendigoit.com.au