It can.  I have seldom had need to worry about it.  Most data centers have battery backups to keep power outages from crashing systems. I am also not sure if its any more or less of a risk than iscsi, except you may not be able to tell right away.  async works by basically lying to the client about the read/write.  Keep in mind that the read/write may be into a virtual machine in this case.  Even if all packets are accounted for, not completing the full stream of writing could lead to a corrupt VM filesystem anyway.  In my mind, its worth the risk for the speed.  This is also why we do backups.


On Fri, Mar 23, 2012 at 7:48 AM, Morgan Cox <morgancoxuk@gmail.com> wrote:
Thank you Gary.

After re-mounting the NFS share with async it dramatically increased the speed !

I can now create a 10GB virtual disk in 2 mins (rather than 10 mins)

Is using the async option more likely to cause data corruption though ?

Many thanks

Regards 

On 22 March 2012 21:54, Gary Scarborough <virtuallymad@gmail.com> wrote:


On Thu, Mar 22, 2012 at 12:59 PM, Morgan Cox <morgancoxuk@gmail.com> wrote:
Hi.

After my many issues with spice I have finally sorted them out.

Now I am having an issue with the speed of virtual disk creation - when I go to create a virtual disk it takes a long time (far to long to be usable) 

My setup is as following

3 servers:-

1 Frontend (ovirt engine) - Fedora 16    - external + local IP (91.215.xxx.xx + 10.0.0.10)
1 Ovirt node (using the node .iso)   - external + local IP (ovirtmgmt (eth0) - 91.215.xxx.xxx  and LAN (eth1) - 10.0.0.101)
1 NFS storage - external + local IP - I attached the storage using the Local IP (10.0.0.190)

All servers are connected via a Gigabit switch (so speed should be better)

I can scp between servers far faster - I'm almost sure its due to the node ovirtmgmt address being an external (internet ip) and not LAN ip. - therefore the traffic is not just going over the gigabit switch but via the core router in the DC...

Can anyone suggest how I can 'debug' where the slowness is coming from 

On my NFS server I have it setup like (in /etc/exports)

/storage1       *(rw,sync,no_subtree_check)

I had previous tried setting up the node on a LAN IP previously and it caused spice to not work - as the node had no internet access / DNS - I also tried making the frontend server a gateway (and using -  iptables -t nat -A POSTROUTING -j MASQUERADE ) - this also cause spice to not work (as it always tried to connect to the 10.0.0.x address from my desktop - and fail..) 

Any hints/help will be welcomed

Cheers



_______________________________________________
Users mailing list
Users@ovirt.org
http://lists.ovirt.org/mailman/listinfo/users


You could try async instead of sync.  You could also try thin provisioning.

--
Gary Scarborough
IST Lab Manager
Rochester Institute of Technology
Rochester NY




--
Gary Scarborough
IST Lab Manager
Rochester Institute of Technology
Rochester NY