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Re: [Xen-devel] [PATCH] Blktap: Userspace file-based image support. (RFC)

Anthony Liguori wrote:
> Rusty Russell wrote:
>> On Mon, 2006-06-19 at 09:19 -0700, Andrew Warfield wrote:
>>> Attached to this email is a patch containing the (new and improved)
>>> blktap Linux driver and associated userspace tools for Xen.  In
>>> addition to being more flavourful, containing half the fat, and
>>> removing stains twice as well as the old driver, this stuff adds a
>>> userspace block backend and let you use raw (without loopback), qcow,
>>> and vmdk-based image files for your domUs.  There's also a fun little
>>> driver that provides a shared-memory block device which, in
>>> combination with OCFS2, represents a cheap-and-cheerful fast shared
>>> filesystem between multiple domUs.
>> Hi Andrew,
>>     I like the idea of block servers in userspace, but I'm curious. 
>> When I
>> wrote the simple share block server I couldn't see an obvious
>> justification for multiple outstanding requests (with AIO/threads and
>> all that entails),
> Are you thinking of posix-aio?  posix-aio is "emulated" with threads and
> normal read/select calls.  The performance isn't that great.


We develop another implementation of posix I/O for linux with better
performance, based on linux kernel AIO, have a look at:


Laurent Vivier
Bull, Architect of an Open World (TM)

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