Read Performance issue when Xen Hypervisor is activated

[Michael Schinzel <schinzel@ip-projects.de>]

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Hello,

first of all, mary christmas for all which read this email to mailinglist.

Since about 14 days, i have a problem with an Xen vServer Host. Hardware Specs:

2x Intel Xeon E5-2620v2
256 GB DDR3 ECC Reg Memory
6x 3 TB WD RE Drives – RAID 10 – HDD Array
2x 256 GB SSDs – RAID 1 – SWAP Drives
2x 600 GB SAS HDDs – RAID 1 – Backup Temp
2x 1 TB SSDs – RAID 1 – xCacheCade
LSI MegaRAID 9361-8i
MegaRAID Kit LSICVM02

When i boot the Server – OS: Debian 8 – with an Kernel without Xen Hypervisor Support, i get the following Performacne at the RAID 10 HDD Array – the test Script is from: http://blog.tdg5.com/tuning-dd-block-size/ -


root@v7:~# ./dd_obs_test.sh datei
block size : transfer rate
     512 : 293 MB/s
    1024 : 469 MB/s
    2048 : 603 MB/s
    4096 : 812 MB/s
    8192 : 866 MB/s
   16384 : 845 MB/s
   32768 : 875 MB/s
   65536 : 929 MB/s
  131072 : 923 MB/s
  262144 : 898 MB/s
  524288 : 956 MB/s
1048576 : 883 MB/s
2097152 : 956 MB/s
4194304 : 925 MB/s
8388608 : 879 MB/s
16777216 : 811 MB/s
33554432 : 826 MB/s
67108864 : 753 MB/s

root@v7:/home#
time dd if=/dev/zero of=datei bs=1M count=10240
10240+0 Datens㳺e ein
10240+0 Datens㳺e aus
10737418240 Bytes (11 GB) kopiert, 26,3243 s, 408 MB/s

real 0m26.327s
user 0m0.012s
sys 0m17.140s

root@v7:/home#
time dd if=datei of=/dev/null
20971520+0 Datens㳺e ein
20971520+0 Datens㳺e aus
10737418240 Bytes (11 GB) kopiert, 11,7919 s, 911 MB/s

real 0m11.794s
user 0m2.612s
sys 0m9.176s


the read performance from the cache goes up to 1.2 – 1.6 Gb/s

When i reboot the Server and boot an kernel with Hypervisor Support, i get the following performance information:

root@v7:~# ./dd_obs_test.sh datei
block size : transfer rate
     512 : 9 MB/s
    1024 : 163 MB/s
    2048 : 256 MB/s
    4096 : 368 MB/s
    8192 : 490 MB/s
   16384 : 569 MB/s
   32768 : 618 MB/s
   65536 : 684 MB/s
  131072 : 717 MB/s
  262144 : 709 MB/s
  524288 : 715 MB/s
1048576 : 742 MB/s
2097152 : 728 MB/s
4194304 : 730 MB/s
8388608 : 696 MB/s
16777216 : 655 MB/s
33554432 : 626 MB/s
67108864 : 558 MB/s


root@v7:/home#
time dd if=/dev/zero of=datei bs=1M count=10240
10240+0 Datensätze ein
10240+0 Datensätze aus
10737418240 Bytes (11 GB) kopiert, 31,6254 s, 340 MB/s

real 0m31.712s
user 0m0.040s
sys 0m15.744s

root@v7:/home#
time dd if=datei of=/dev/null
20971520+0 Datensätze ein
20971520+0 Datensätze aus
10737418240 Bytes (11 GB) kopiert, 50,6099 s, 212 MB/s


I have upgraded Controller Firmware, BIOS, changed mainboard, changed hard drives, changed RAID Controller. I can not find the reason why the performance of the hypervisor kernel is such bad.

I have tested Kernel 4.9, Kernel 4.4 and Kernel 3.16.36 default debian. All Versions such the same values.

Installed ist he default Hypervisor Version 4.4.1. Has anybody the same problem and could help me to solve it?


Yours sincerely

Michael Schinzel


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