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Benefits to blktap2 over the old version of blktap:
* Isolation from xenstore - Blktap devices are now created directly on
the linux dom0 command line, rather than being spawned in response
to XenStore events. This is handy for debugging, makes blktap
generally easier to work with, and is a step toward a generic
user-level block device implementation that is not Xen-specific.
* Improved tapdisk infrastructure: simpler request forwarding, new
request scheduler, request merging, more efficient use of AIO.
* Improved tapdisk error handling and memory management. No
allocations on the block data path, IO retry logic to protect
guests
transient block device failures. This has been tested and is known
to work on weird environments such as NFS soft mounts.
* Pause and snapshot of live virtual disks (see xmsnap script).
* VHD support. The VHD code in this release has been rigorously
tested, and represents a very mature implementation of the VHD
image
format.
* No more duplication of mechanism with blkback. The blktap kernel
module has changed dramatically from the original blktap. Blkback
is now always used to talk to Xen guests, blktap just presents a
Linux gendisk that blkback can export. This is done while
preserving the zero-copy data path from domU to physical device.
These patches deprecate the old blktap code, which can hopefully be
removed from the tree completely at some point in the future.
Signed-off-by: Jake Wires <jake.wires@citrix.com>
Signed-off-by: Dutch Meyer <dmeyer@cs.ubc.ca>
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