Paravirtualized machine hanging (VM Server 2.1, NFS based repository)

Question

Hi,
I have a problem with a VM server.
I have local disks, that are kind of slow (initially my images were on OCFS2 based /OVS, after some problem with it wi migrated /OVS to ext3), but because of insufficient space we want to use NFS.
I created an NFS repository with:
/usr/lib/ovs/ovs-makerepo 172.16.32.51:/lv_raid5_fs1/OVS 1 raid5_nfs
then I created a HVM wirtual machine with OEL4U5 (using installation from ISO images) - it works relatively fine (it hanged just once).
I tried creating a PVM from the template OVM_EL4U5_X86_PVM_10GB.
I did that using Oracle VM Manager. The template was created, and after the Power On command the VM started.
I then wanted to test disk operations performance with simple
dd if=/dev/zero of=/root/test_prs.dat bs=1048576 count=3000
but it actually hanged (domU hanged, the iostat command that I had started continue to work though - showing no IO operations were going on, but iowait is 100%.
Also xentop in dom0 hanged - it didn't refresh for 12 hours.
The whole dom0 doesn't respond to new ssh requests (the existing one with xentop is not closed).
The domU with the PVM allowed me to run some commands in another open sheel via ssh, but then it hang also..
The NFS server I am using is a SLES9 SP3 + online updates (2.6.5-7.276-bigsmp). It is attached to SCSI Storage array.
The exportfs options are "(rw,wdelay,no_root_squash)". The exported filesystem is reiserfs.
The mount options in dom0 are "vers=3,tcp", I cannot find them all right now, because the dom0 is hanged.
the connection between NFS client and server is 1Gbit.
NFS Server hasn't shown any errors.
The last screen from xentop is below:
xentop - 19:31:19 Xen 3.1.1
3 domains: 1 running, 2 blocked, 0 paused, 0 crashed, 0 dying, 0 shutdown
Mem: 8387988k total, 3825360k used, 4562628k free CPUs: 8 @ 1995MHz
NAME STATE CPU(sec) CPU(%) MEM(k) MEM(%) MAXMEM(k) MAXMEM(%) VCPUS NETS NETTX(k) NETRX(k) VBDS VBD_OO VBD_RD VBD_WR 90_soa b- 362 0.1 2097152 25.0 2097152 25.0 2 1 34083 3236 1 0 20981 45823 VBD BlkBack 768 [ 3: 0] OO: 0 RD: 20981 WR: 45823
Domain-0 -----r 286 1.7 524288 6.3 no limit n/a 8 8 2461308 2509950 0 0 0 0 linux_hv_1 b- 268 2.3 1056644 12.6 1064960 12.7 1 1 0 0 1 0 0 0 VBD BlkBack 768 [ 3: 0] OO: 0 RD: 0 WR: 0
Now my time is 11:26:00 (so more than 15 hours - no refresh of the screen). We've seen such a behaviour previously, but after 20-30 minutes it all started working again.
What can I do to improve the situation? What could be the problem?
Please help...
Regards,
Mihail Daskalov

Answer 1

Hi,
1) What does it mean "supported" - there are no specific requirements published. As I said my "filer" is another Linux machine which is exporting a file system via NFS.
2) I already tested the NFS using another real machine (not a virtualized one) and it works perfect. I also tested the NFS mount point from dom0 on the same VM server and it worked...
3) I have problem with the paravirtualized machine (from template)
any other suggestions?