[Xen-devel] COW in Xen

["Mark Ryden" <markryde@xxxxxxxxx>]

Hello,

I had posted this question in Xen-user mailing list three days ago and I did not
get a single answer. On a second thought, maybe xen-devel is more
appropriate so
I am trying again in the hope that I will receive an answer:

Does anybody have an experience (good or bad) with using
COW (Copy-On-Write) storage in Xen ?

I saw that there is a (rather small) wiki page about it :
http://wiki.xensource.com/xenwiki/COWHowTo

And also some instructions from Michael Lang for using
unionfs for COW for Xen:
http://wiki.xensource.com/xenwiki/InstructionsFromMichaelLang

My question is :
There are some altenatives which are discussed in that wiki page:
unionfs, blktap ,using qemu: see
http://lxr.xensource.com/lxr/source/tools/blktap/,
BenRin's Copy-on-Write md device,Translucency , DmUserspace
,parallax, CowNFS , and LVM snapshots (According to MichaelVrable wiki
as I understood it).
And BTW- does the XenFS has (or is intended to have) COW support ?

What are the pros and cons of these options ? is there a  preferred
one when using Xen ?

Regards,
Mark Ryden

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