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I am kind of new to the world of virtualization...I am doing some tests using different tools (iometer, fio, dd tool, and bonnie++). The idea is to benchmark the disk performance for different operating systems in a virtualized environment and for different types of virtualization (Paravirt. and Full-virt.).
The results out of those tests for Windows (XP, 7 and 8) were not as I expected with almost all tools, since I got a relatively high performance results without installing the paravirt. drivers for Windows, and what was more surprisingly that after installing the paravirt. drivers the performance decreased.
Samples of my tests using fio tool:
Writing a sequential file the with size of 16 GB and with block size of 512 KB
Windows 7 (Full-Virt.): 87.2 MB/s average aggregate bandwidth
Ubuntu (Paravirt.): 72.9 MB/s average aggregate bandwidth
Any ideas about what is going on here (I am using openSUSE as an OS in case it matters) !!
Accepted AnswerEdelweissOffline0Can you clarify a little:
When you say that perf went down "after installing paravirt" you don't give any performance figures for windows with PV drivers. I am also confused what the figure "installing PV ubuntu" means.
Also, which windows PV drivers have you used? Citrix, GPLPV, Novell / Suse?.
Not sure if Ubuntu PV means PV or PVHVM.
Note that the disk backend in use can make a big difference to performance. So any more information woul dhelp.
Which version of openSUSE is being used?
Depending on the configuration, emulated devices can be hitting the buffer cache in dom0, which can be fast but is not safe (i.e. after a power cut your data can be toast). The logic here is that emulated can be cached/unsafe because you only use it while installing and then switch to PV drivers. More information on the config may be helpful.
Accepted AnswerMahmoudOffline0Thanks for your respond, and as I said I am new to this field so I hope you bear with me
Actually the results I have mentioned before (87.2 MB/s average aggregate bandwidth) was for Windows 7 (64 bits) with the pv drivers which is GPLPV.
Before installing the drivers the results was 92.8 MB/s average aggregate bandwidth.
And to be honest I am confused between the terms PV and PVHVM, what I did is that I created a VM (Ubuntu 12.04 64 bits) in full virtualization type then using the same disk of this VMI created another VM in paravirtualization type, so as I far as I understand this is PV !!
OpenSUSE version is 12.3 and Xen version is 4.2.1
What kind of information should I be looking for in the configuration file ?! But isn't enough that I am using file size (16 GB) greater than my cache (2 GB). Also the tool I am using (fio) has the ability to enable or disable buffering or caching.
fio --name=job --rw=write --filesize=16gb --blocksize=512kb --direct=1 --fsync=1 --buffered=0
I am using the same command for both VM.
Thanks so much for your help.