Hi!
I have a question about nfs-performance. I don't where the problem is.
My setup:
Host dom0 with 8TB harddisk space 8GB RAM and 6 core CPU.
The hard disk raid is fast:
<cut>
root@midas-phalanx:/data# time dd if=/dev/zero of=test.null bs=1M count=1024
1024+0 Datensätze ein
1024+0 Datensätze aus
1073741824 Bytes (1,1 GB) kopiert, 3,27874 s, 327 MB/s
real 0m3.303s
user 0m0.004s
sys 0m1.792s
</cut>
so the write performance is very good on harddisk.
I created several domU guests which do a nfs-boot from the local host.
(strange setup, I know). I don't want to define the size of guests disk
so I don't want to use a image as hard disk image. This is why I do a
nfs-boot.
The dom0 exports the file system for the guest. I use network bridging.
My guest config file is the following:
<cut>
kernel = '/boot/vmlinuz-2.6.32-5-xen-amd64'
ramdisk = '/boot/initrd.img-2.6.32-5-xen-amd64'
memory = 1024
name = 'ufp-mysql-01'
hostname = 'ufp-mysql-01'
#dhcp = 'dhcp'
vif = [ 'mac=00:16:3e:00:42:06, bridge=lan' ]
interface = 'eth0'
ip = '10.10.42.206'
netmask = '255.255.255.0'
gateway = '10.10.42.204'
nfs_server = '10.10.42.108'
nfs_root = '/data/nfs-root/ufp-mysql-01'
root = '/dev/nfs'
extra = '2 console=hvc0 xencons=tty boot=nfs rootfstype=nfs'
</cut>
The guest boots without error. But the write performance over the nfs is
very poor:
<cut>
root@ufp-mysql-01:~# time dd if=/dev/zero of=test.null bs=1M count=512
512+0 Datensätze ein
512+0 Datensätze aus
536870912 Bytes (537 MB) kopiert, 2159,08 s, 249 kB/s
real 35m59.133s
user 0m0.000s
sys 0m1.396s
</cut>
The read-performance is good:
<cut>
root@ufp-mysql-01:~# dd if=test.null of=/dev/zero bs=1M
512+0 Datensätze ein
512+0 Datensätze aus
536870912 Bytes (537 MB) kopiert, 0,705893 s, 761 MB/s
</cut>
But it is not the performance of the server itself:
<cut>
root@ufp-mysql-01:~# dd if=/dev/zero of=/dev/null bs=1M count=512
512+0 Datensätze ein
512+0 Datensätze aus
536870912 Bytes (537 MB) kopiert, 0,0655885 s, 8,2 GB/s
</cut>
OK, this is the setup where the nfs-server is on dom0 and exports the
filesystem for domU.
When I copy the rootfs to another computer and export it from there
(with same export options) I get a lot of more performance.
This is the guest bootet from nfs on other server:
<cut>
root@ufp-mysql-01:~# time dd if=/dev/zero of=test.null bs=1M count=512
512+0 Datensätze ein
512+0 Datensätze aus
536870912 Bytes (537 MB) kopiert, 15,506 s, 34,6 MB/s
real 0m15.617s
user 0m0.004s
sys 0m1.260s
</cut>
The "external" nfs-server has a single hard disk, so this performance is
OK for this config.
Can you give me a hint why the perfmance is so bad when I export the fs
from dom0? How can i solve this?
The server has no I/O jobs while this test was running so the whole
performance should be available.
Jens
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