Samuel Torton
2006-Feb-24 12:37 UTC
[Xen-users] Crash: domU NFS server hosting domU filesystems
Hi,
We have two physical machines "host1" and "host2", IBM
Bi-pro Xeon 3.0 Ghz +
RAM 3 GB, each running Xen 3.0.1, and hosting domU machines.
- dom0: "host1": RAM 512 MB + LVM filesystem
- dom0: "host2": RAM 512 MB + NFS client
-1- First config and performed tests:
-------------------------------------
--> "host1" dom0 machine hosts a domU machine "guest1"
. "guest1" is a NFS server
--> "host2" has a mount on "guest1" NFS server
|---------------------------| |---------------------------|
| dom0: "host2" | | dom0: "host1"
|
| RAM: 512MB | | RAM: 512MB |
| | | |
| NFS client | | LVM |
| + mount on "guest1" | | |
| /nfs/guest1/data | | |
|---------------------------| |---------------------------|
| |
| |---------------------------|
| | domU: guest1 |
| | RAM: 512MB |
| | |
|----------------------|-----> NFS server |
| /data |
| |
|---------------------------|
Tests from "host2":
create files in /nfs/guest1/data folder, with "dd" command.
example: --> dd if=/dev/zero of=/nfs/guest1/data/x.fs bs=1024k count=xxxxx
I am able to create very huge files (up to 10 GB and more...), and all the
machines (dom0 and domU) behave correctly, without crashing.
With this kind of tests, I can say I''m confident with NFS server and
client
config.
Now, I will do the following tests...
-2- Second config and performed tests:
--------------------------------------
I have exactly the same config as step -1-, but I''m adding a new domU
machine named "guest2".
--> "guest1" NFS server stores the domU "guest2"
filesystems
(root.fs, data.fs, var.fs, swap.fs, etc...)
--> "host2" dom0 machine runs the domU machine "guest2"
the Xen guest2.cfg looks like this:
...
disk = [''file:/nfs/guest1/data/guest2/root.sfs,sda1,w'',
''file:/nfs/guest1/data/guest2/swap.sfs,sda2,w'',
''file:/nfs/guest1/data/guest2/tmp.sfs,sda3,w'',
''file:/nfs/guest1/data/guest2/var.sfs,sda4,w'',
''file:/nfs/guest1/data/guest2/data.sfs,sda5,w'']
...
|---------------------------| |---------------------------|
| dom0: "host2" | | dom0: "host1"
|
| RAM: 512MB | | RAM: 512MB |
| | | |
| NFS client | | LVM |
| + mount on "guest1" | | |
| /nfs/guest1/data | | |
|---------------------------| |---------------------------|
| |
|---------------------------| |---------------------------|
| domU: "guest2" | | domU: "guest1"
|
| RAM: 512MB | | RAM: 512MB |
| | | |
| | | NFS server |
| |-----|----->/data/guest2/*.fs |
| | | |
|---------------------------| |---------------------------|
Tests from "guest2":
create files in /data folder, with "dd" command.
example: --> dd if=/dev/zero of=/data/x.fs bs=1024k count=xxxxx
I am able to create files, but if i try to create files bigger than 100 or
200 MB, I get a very big crash on domU "guest2" machine, and even on
dom0
"host2" machine !!! It''s not really a crash, but both
machines totally
freeze.
"host1" and "guest1" are not impacted at all,
but I can''t do anything on "host2" and "guest2... except
rebooting manually
the physical machine !!
I''m pretty convinced it''s a Xen bug, but I would like to have
confirmation
from Xen team ?
Do you think this issue will be solved in Xen 3.0.2 release ?
Here are some other hints:
- If I increase RAM size on "host2", the crash still happens;
- If I swapoff "host2" and "guest2", the crash still
happens;
- I thought to have found a workaround to avoid the crash, but it still
crashes:
in the "guest2" /etc/fstab file, I set ALL disk options to
"sync"
--> performances are totally degraded, and still crashes with bigger files
!
Thank you for your help,
Samuel
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