Xen DomU’s I/O Performance of LVM and loopback Backed VBDs

This posts list benchmark (using bonnie++) result of I/O performance of Xen LVM and loopback backed VBDs.

The configuration of machines

Dom0

VCPU: 2 (Intel(R) Xeon(R) CPU E5520  @ 2.27GHz)
Memory: 2GB
Xen and Linux kernel: Xen 3.4.3 with Xenified 2.6.32.13 kernel

DomU

VCPU: 2
Memory: 2GB
Linux kernel: Fedora (2.6.32.19-163.fc12.x86_64)

DomU’s profile:

name=”10.0.1.200″
vcps=2
memory=2048
disk = [‘phy:vg_xen/vm-10.0.1.150/vmdisk0,xvda,w’]
#disk = [‘tap:aio:/lhome/xen/vm0-f12/vmdisk0,xvda,w’]
#disk = [‘file:/lhome/xen/vm0-f12/vmdisk0,xvda,w’]

vif=[‘bridge=eth0′]
bootloader=”/usr/bin/pygrub”
#extra=”single”
on_reboot=’restart’
on_crash=’restart’

The “disk” lines is changed depending on the driver used.

Benchmark method

We use Bonnie++ to test the performance of I/O:

# bonnie++ -u root

We run bonnie++ on one single VM. We also test the performance change after making a snapshot of LVM for a new VM. For the file backed VMs, we also run two VMs together on the same hard disk and run bonnie++ on them.

Bonnie++’s result is in this format:

Version 1.03e       ------Sequential Output------ --Sequential Input- --Random-
 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
localhost.locald 4G 76999  98 107423  21 47522  13 73347  91 159847  16 266.0   0
 ------Sequential Create------ --------Random Create--------
 -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
 files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
 16 +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++ +++++ +++
localhost.localdomain,4G,76999,98,107423,21,47522,13,73347,91,159847,16,266.0,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

We only list the last line which contains all the result in the result section in this post.

Benchmark result

LVM backed VBD

localhost.localdomain,4G,76999,98,107423,21,47522,13,73347,91,159847,16,266.0,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,79588,98,120078,22,46140,13,75343,94,150167,15,248.7,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,81942,98,113617,22,47736,13,75947,94,152110,15,262.1,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

New LVM logical volume made by snapshot

localhost.localdomain,4G,11846,15,12044,2,27133,7,71510,92,141408,14,262.7,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,12200,15,18147,3,33086,9,66687,89,146550,14,251.9,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,58521,73,58482,10,33880,9,69399,90,144237,14,267.4,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,62553,78,57576,11,32755,9,70037,89,143462,14,259.9,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,66031,84,65640,12,34357,9,66036,86,152171,15,266.4,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
localhost.localdomain,4G,58666,75,60092,11,34826,9,72821,91,141328,14,259.7,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

File backed VBD

vm112,4G,20865,27,23559,4,32913,9,63006,81,128395,13,217.9,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,23022,30,18611,3,30086,8,63784,82,125736,13,197.7,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,21485,27,20366,3,29587,8,72130,92,140957,14,239.6,0,16,+++++,+++,+++++,+++,30751,52,+++++,+++,+++++,+++,+++++,+++
vm112,4G,22375,32,21716,3,30300,8,65488,87,128625,13,221.4,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,21968,28,19298,3,29007,8,68469,88,122111,12,222.5,0,16,26967,94,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,21477,28,20463,3,38395,10,49312,63,154206,15,241.0,0,16,+++++,+++,+++++,+++,32699,56,+++++,+++,+++++,+++,+++++,+++

Two VMs on the same disk running together

A:

vm112,4G,10645,13,9498,1,9606,2,30866,41,86911,8,100.1,0,16,9181,22,20583,6,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,10623,13,10143,1,10485,2,26013,35,77362,7,116.3,0,16,25701,66,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,10824,14,9558,1,12028,3,27503,36,57196,5,92.1,0,16,9679,28,+++++,+++,9294,15,+++++,+++,+++++,+++,+++++,+++
vm112,4G,15098,19,10485,1,12536,3,22771,30,64679,6,142.2,0,16,32006,82,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,11315,14,9674,1,12052,3,26453,35,68206,7,121.1,0,16,23789,62,32446,13,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm112,4G,11865,15,11564,2,11508,3,24945,34,61946,6,102.6,0,16,13297,34,21805,7,+++++,+++,+++++,+++,+++++,+++,+++++,+++

B:

vm119,4G,8963,11,9255,1,10909,3,36446,48,70485,7,125.1,0,16,19701,52,23649,8,9574,16,+++++,+++,+++++,+++,+++++,+++
vm119,4G,9074,12,8410,1,12898,3,35266,47,68469,7,107.4,0,16,6585,17,3206,1,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm119,4G,9151,13,8664,1,10285,2,20120,28,58011,5,90.9,0,16,22894,59,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm119,4G,9053,11,10406,1,12852,3,27618,37,55405,5,108.8,0,16,10144,24,22599,7,+++++,+++,+++++,+++,+++++,+++,+++++,+++
vm119,4G,8987,11,11464,1,12123,3,19278,26,59274,6,104.8,0,16,5357,13,23010,7,+++++,+++,7922,18,+++++,+++,+++++,+++
vm119,4G,9593,12,11450,1,30598,8,57078,73,119884,12,222.2,0,16,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++,+++++,+++

Conclusion

From the evaluation results, we can see that LVM backed VBD of Xen DomU has a much better performance than file backed VBD. From our experiment with Xen with LVM for more than 2 years in our cluster, LVM backed VBD is also quite stable.

Eric Zhiqiang Ma

Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.

3 comments:

  1. Hello,

    What is the recommended base configuration for XEN Host and VM in Centos 7.2?

    On server total we have 3 hard disk, 2 x 2 TB and 240Gb SSD.

    Our setup is like host(dom0) on 2 TB HDD and VM (domU) on SSD.

    On host (2 TB HDD) – partition is like /boot and rest of the partition on LVM.
    On SSD – Virtual Machine (domU) is also LVM.

    So now concern both dom0 and domU is on LVM so does it create I/O performance issue?

    Thanks,
    Nishit Shah

  2. Thank You.

    Another Question?
    I have created two guest VM on SSD drive with Centos 7.2. SSD drive is on LVM. Now inside first VM partition is LVM based XFS filesystem and inside second VM partition is standard based XFS filesystem.
    The boot time of first VM is around 4 to 5 minutes and second VM boots in less than 30 seconds.
    The boot time of first VM is really worried me on production server. Is it because of partition created on LVM inside first VM? Inside first VM console I have notice that xenbus_probe_frontend
    hangs the OS boot for up to 5 minutes as it check some devices on system.
    Any idea how to fix this or some workaround?

    Thanks,
    :Nishit Shah

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