[Xen-users] Re: Differences in performance between file and LVM based images

[Ligesh <myself@xxxxxxxxxx>]

 Hey,

  I didn't know that my question would actually provoke so much discussion. I 
had thought this would be a semi-settled issue. See, the whole thing sort of 
becomes moot when you consider the fact that nowadays people use LVM for their 
normal partitioning itself. So whether you use LVM or file based storage, the 
LVM overhead would always be there. When you use file based storage, the logic 
first has to go through the ext3, then through the LVM and then to the 
harddisk. So LVMs simply win by default.

  Anyway, some more benchmarks would be welcome. Of course, giving dom0 1GB 
memory is silly, since dom0 is not supposed to be doing any "useful" work. The 
aim is not even performance, but rather scalability. At least as far as I am 
concerned (and also the purported aim of Xen being to improve server 
utilization from 15% to 85%)--which is data center virtualization--the idea is 
to have as many domUs as possible on a single server, and this is important, 
especially if xen want to be comparable to container technologies like solaris 
zones or openvz. In fact, I would appreciate if someone could do some 
benchmarks on xen vz openvz or solaris zones, and see what exactly are the 
performance penalties and how they can be overcome, if at all. The clear 
overhead that I can see is the memory needed for the domU kernel, but I don't 
think this is really too much, and also this can be further reduced by 
compiling custom domU kernels. I would also like to know if there are any other 
areas where Xen would _significantly_ trail in performance when compared to OS 
level virtualization.


 Thanks

--
:: Lxhelp :: lxhelp.at.lxlabs.com :: http://lxlabs.com :: 



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