Why can't nfs remount after disconnect?

[Gabrie1]

Hi

Home environment with only one cable to my small NFS NAS. Strange thing is that when I pull the cable from the NAS and then plug it in again, the ESX hosts cannot reconnect. Only thing that works is to unmount and remount the NFS store on each host. I usually do it by command line with the esxcfg-nas option, but I'm surprised ESX can't recover from this. Why is that?

I also have a small iSCSI NAS and there are no problems reconnecting. Just do a rescan at cluster level and we're back.

http://www.GabesVirtualWorld.com

[DSTAVERT]

It is more about the NFS protocol than anything else.

[Gabrie1]

ok, but would you say that this can't be solved? How can an enterprise use NFS reliable then?

http://www.GabesVirtualWorld.com

[DSTAVERT]

I use NFS and generally don't have issues. A lost connection usually re establishes itself when it is reconnected, without the need to rescan. I have had a recent incident where the NAS rebooted and when it cam back online not only did it reconnect but several of the VMs were still running. Very little activity of course.

NFS generally isn't that good at detecting connection dropouts since it is UDP. Not waiting for ACKs etc. I don't know what mechanism anyone uses for detecting lost connectivity or reconnection.

What are you using for NFS.

[oreeh]

FYI: ESX only uses NFS over TCP

[Gabrie1]

Its an Iomega IX2-200 StorCenter. And although I don't expect high performance from it, it is VMware certified and I wouldn't expect these dropouts.

https://iomega-eu-en.custhelp.com/cgi-bin/iomega_eu_en.cfg/php/enduser/std_adp.php?p_faqid=22139

http://www.GabesVirtualWorld.com

[DSTAVERT]

Sorry about the UDP reference. I have been using UDP with some LINUX backup testing all week.

The switch?

Have a look through the NFS FAQ's on sourceforge. See if there is anything you can relate to.

[Gabrie1]

Hmmm you think it could be the switch I'm using?

I can try and hang it on a 100Mbit Cisco 3550. I bought a soho 8port Gigabit switch especially for my esx hosts and NAS. (Linksys SLM2008)

http://www.GabesVirtualWorld.com

[DSTAVERT]

The switch, the cable? What settings do you have available for NFS?

[Gabrie1]

On the NFS settings, I can only turn it on or off.

I will play with the switch and see if that changes things.

Thx

http://www.GabesVirtualWorld.com

[jasoncllsystems]

Personally, I have the experienced which NFS 'unmount' option go missing and after refresh on particular NFS datastore then only 'unmount' option display on the screen. I would said probably VCenter bug.

Regards,

Jas

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[esloof]

NFS is a great storage solution within a VMware vSphere environment but when the connection to the NFS server is lost, you’re in big trouble. In most circumstances some virtual machines are still connected to the NFS Datastore and since it’s in use, you cannot delete and recreate it. I’ve tried this by using the vClient and trough the command line but didn’t succeed. In the end there’s no other alternative than rebooting the ESX host, or is there…. If you want to find out how to remount an NFS Datastore you better watch this online training.

http://www.screencast.com/users/esloof/folders/Online-Training