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Re: [Xen-users] tap:ram anyone?


  • To: "Dylan Martin" <dmartin@xxxxxxxxxxxx>
  • From: "Todd Deshane" <deshantm@xxxxxxxxx>
  • Date: Fri, 9 Jan 2009 22:20:52 -0500
  • Cc: xen-users <xen-users@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Fri, 09 Jan 2009 19:21:48 -0800
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On Fri, Jan 9, 2009 at 5:42 PM, Dylan Martin <dmartin@xxxxxxxxxxxx> wrote:
> Has anyone ever tried the 'ram' driver with blktap for block devices?
> It's mentioned here:
>
>  http://wiki.xensource.com/xenwiki/blktap
>
>    Fast shareable RAM disk between VMs (requires some form of
> cluster-based filesystem support e.g. OCFS2 in the guest kernel)
>
> and poking around the source, in tools/blktap there is a README
> (almost identical to the above web page) and the drivers themselves.
>
> I've been trying to get it to work on CentOS 5.2 to no avail.  Specifically:
>
>   block-attach domain 'tap:ram:/path/to/file' hdb w
>
> ..makes something appear in the output of block-list, but the domU
> doesn't react at all.  (nothing in dmesg, /dev/dhb is not found
> etc...)  Sadly, this is exactly the same thing that happens if you
> specify a bogus tap driver, (EG tap:wibble:/path/to/file).
>
> I've tried tap:aio and tap:sync and they both work.
>

I haven't tried it personally.

There has been very little development on it.

see:
http://lxr.mstier.de/Xen/source/xen_3.2.1/tools/blktap/drivers/block_ram.c?v=3.2.1
http://xen.markmail.org/search/?q=block_ram.c

Maybe some hints in the code and/or changes since the CentOS Xen version.

Cheers,
Todd

-- 
Todd Deshane
http://todddeshane.net
http://runningxen.com

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