使用Glusterfs作为kvm后端存储

Glusterfs已经发布到3.4版本了,据称红帽针对vm储存做了优化使其更适合用于虚拟化存储.本文测试使用Glusterfs作为kvm后端存储,通过直接调用glustefs-api,绕过fuse访问虚拟机镜像,避免了fuse带来的性能损耗.

1.测试环境

centos6.4 x86-64

gluster-3.4

qemu-1.5.2

机器:

192.168.1.100:glusterfs+kvm

192.168.1.101-103:glusterfs

2.Glusterfs存储集群部署

gluster集群部署完毕后,创建一个volume用于存放vm镜像

gluster volume create vm-images stripe 2 replica 2  192.168.1.{100,101,102,103}:/data/vm-images
gluster volume start vm-images

3.虚拟化机器上安装qemu
centos6自带的qemu1.2版本并不支持glusterfs,这里要编译新版的qemu.

安装qemu前先装上glusterfs-devel

rpm –ivh http://download.gluster.org/pub/gluster/glusterfs/3.4/3.4.0/CentOS/epel-6Server/x86_64/glusterfs-devel-3.4.0-8.el6.x86_64.rpm

安装依赖的包

 yum install zlib-devel glib2-devel -y

开始编译qemu,加上参数--enable-glusterfs

wget http://wiki.qemu-project.org/download/qemu-1.5.2.tar.bz2 
tar jxvf qemu-1.5.2.tar.bz2 
cd qemu-1.5.2 
./configure --enable-glusterfs  #这里加上enable-glusterfs 
make;make install

4.使用

环境安装完毕,使用qemu-img创建一个虚拟机磁盘

/usr/local/bin/qemu-img create -f qcow2 gluster://192.168.1.100/vm-images/disk1 10G

创建一个虚拟机

qemu-system-x86_64 --enable-kvm -m 1024 -drive file=gluster://192.168.1.100/vm-images/disk1 -vnc :15 -cdrom /data/CentOS-6.4-i386-minimal.iso

现在可以使用VNC连上并安装系统了.

5.后记

qemu连接glusterfs支持多种格式:

gluster://1.2.3.4/testvol/a.img 
gluster+tcp://1.2.3.4/testvol/a.img 
gluster+tcp://1.2.3.4:24007/testvol/dir/a.img 
gluster+tcp://[1:2:3:4:5:6:7:8]/testvol/dir/a.img 
gluster+tcp://[1:2:3:4:5:6:7:8]:24007/testvol/dir/a.img 
gluster+tcp://server.domain.com:24007/testvol/dir/a.img 
gluster+unix:///testvol/dir/a.img?socket=/tmp/glusterd.socket 
gluster+rdma://1.2.3.4:24007/testvol/a.img

经过测试发现qemu连接glusterfs是支持高可用的,如gluster://1.2.3.4/testvol/a.img,1.2.3.4宕机将不会影响虚拟机运行.

另外测试过程发现gluster对xfs分区格式兼容性不是太好,会有使用空间大小不正确的现象,解决方法是:

gluster volume set  cluster.stripe-coalesce enable

6.附上老外的性能测试

由测试结果可以看到使用api连接glusterfs性能比fuse提高近一倍,并且接近本地磁盘的速度.

The following numbers from FIO benchmark are to show the performance advantage of using QEMU’s GlusterFS block driver instead of the usual FUSE mount while accessing the VM image.

Test setup

Host Dual core x86_64 system running Fedora 17 kernel (3.5.6-1.fc17.x86_64)
Guest Fedora 17 image, 4 way SMP, 2GB RAM, using virtio and cache=none QEMU options

QEMU options

FUSE mount qemu-system-x86_64 –enable-kvm –nographic -smp 4 -m 2048 -drive file=/mnt/F17,if=virtio,cache=none => /mnt is GlusterFS FUSE mount point
GlusterFS block driver in QEMU (FUSE bypass) qemu-system-x86_64 –enable-kvm –nographic -smp 4 -m 2048 -drive file=gluster://bharata/test/F17,if=virtio,cache=none
Base (VM image accessed directly from brick) qemu-system-x86_64 –enable-kvm –nographic -smp 4 -m 2048 -drive file=/test/F17,if=virtio,cache=none => /test is brick directory

FIO load files

Sequential read direct IO ; Read 4 files with aio at different depths
[global]
ioengine=libaio

direct=1
rw=read
bs=128k
size=512m
directory=/data1
[file1]
iodepth=4
[file2]
iodepth=32
[file3]
iodepth=8
[file4]
iodepth=16
Sequential write direct IO ; Write 4 files with aio at different depths
[global]
ioengine=libaio

direct=1
rw=write
bs=128k
size=512m
directory=/data1
[file1]
iodepth=4
[file2]
iodepth=32
[file3]
iodepth=8
[file4]
iodepth=16


FIO READ numbers

aggrb (KB/s) minb (KB/s) maxb (KB/s)
FUSE mount 15219 3804 5792
QEMU’s GlusterFS block driver (FUSE bypass) 39357 9839 12946
Base 43802 10950 12918

FIO WRITE numbers

aggrb (KB/s) minb (KB/s) maxb (KB/s)
FUSE mount 24579 6144 8423
QEMU’s GlusterFS block driver (FUSE bypass) 42707 10676 17262
Base 42393 10598 15646

Updated numbers

Here are the recent FIO numbers averaged from 5 runs using latest QEMU (git commit: 03a36f17d77) and GlusterFS (git commit: cee1b62d01). The test environment remains same as above with the following two changes:

  • The GlusterFS volume has write-behind translator turned off
  • The host kernel is upgraded to 3.6.7-4.fc17.x86_64

FIO READ numbers

aggrb (KB/s) % Reduction from Base
Base 44464 0
FUSE mount 21637 -51
QEMU’s GlusterFS block driver (FUSE bypass) 38847 -12.6

FIO WRITE numbers

aggrb (KB/s) % Reduction from Base
Base 45824 0
FUSE mount 40919 -10.7
QEMU’s GlusterFS block driver (FUSE bypass) 45627 -0.43

 

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