WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

[Xen-users] Re: performance problem with more than one domain U

----Messaggio originale----
Da: todd.deshane@xxxxxxx
Data: 25/09/2011 4.37

> So the VMs have very different configurations then?
> Have you tried giving the 2 VMs equal resources?
> Why wouldn't you expect a virtual machine with less vCPUs and less memory
> to perform slower?

OK, maybe I did not explain very well the situation in my previous post.

Let's say I have 2 VM, called VM "A" and VM "B"

VM "A" has 8 vcpus and 12 GB RAM

VM "B" has  1 vcpu and 2 GB RAM

Now, I start the VM A and from the VM A I do the command time rm -r  /mydir
and I have this time:

0.15 user 
0.60 system 
3:46.79 elapsed

Then I start the VM "B". I just start it, but I am always logged to VM "A".

At this point I launch another time the command "time rm -r  /mydir" ALWAYS
FROM VM "A", not B!
And, on the same VM, this time I have:
0.00 user 
0.56 system 
15:33.38 elapsed

The only difference is that now domain "B" is running.

>The rm command might not get the best benchmark to to understand what
>is going on. Have you considered testing a microbenchmark like iozone?

I also did the command:

hdparm -tT /dev/mapper/myserver-root

Strange thing, this always perform similar

when the rm command took 8:42 minutes:
 Timing cached reads:   5700 MB in  1.99 seconds = 2857.98 MB/sec
 Timing buffered disk reads:  120 MB in  3.02 seconds =  39.75 MB/sec

when the rm command took 1:27 minutes:
 Timing cached reads:   5466 MB in  1.99 seconds = 2740.00 MB/sec
 Timing buffered disk reads:  146 MB in  3.01 seconds =  48.48 MB/sec


>What is your disk backend and is it the same for each? It is a shared
>directory or are you creating/copying the same directory to each
>machine for the test?

As explained above it is the same VM.

I should add that at hardware level (i.e. dom0) I have an Adaptec Raid Card
with four 2 GB SATA hard disks in a RAID 10 configuration, if that's matter

Thank You for everything

Mario

PS: I am sorry, I have some problem with my webmail. So I posted this 3
times ... :-(

--
View this message in context: 
http://xen.1045712.n5.nabble.com/performance-problem-with-more-than-one-domain-U-tp4833868p4841547.html
Sent from the Xen - User mailing list archive at Nabble.com.

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users

<Prev in Thread] Current Thread [Next in Thread>