On Tue, Sep 22, 2015 at 8:34 PM, Peter Ross <petrosssit@gmail.com> wrote:

Hi Chris,

On Tue, Sep 22, 2015 at 10:38 AM, Chris Samuel <chris@csamuel.org> wrote:

Hi Peter,

On 22/09/15 10:09, Peter Ross wrote:

> I looked around on CentOS 7 - I could not find similar functionality.

According to:

http://www.citi.umich.edu/projects/nfsv4/linux/features.html

delegation support was added to the NFSv4 client in 2.6.9-rc1 and to the
NFS server in 2.6.10, so my suspicion is that it's enabled by default.

The sysctl you are looking for (on RHEL6 at least) is:

[root@snowy-m ~]# sysctl fs.leases-enable
fs.leases-enable = 1

I have to correct myself. You are right, it is part of Linux NFSv4 delegation implementation.

http://wiki.linux-nfs.org/wiki/index.php/Cluster_Coherent_NFSv4_and_Delegations

How the recall gets transmitted is still a mystery to me. If there is no daemon, it must be "inbound" using the TCP port 2049? No, that would cause real trouble when interacting with other NFS servers. Or??

The issues on the page below scare me a bit, especially

http://wiki.linux-nfs.org/wiki/index.php/Server_4.0_and_4.1_issues#Callback_failure_handling

May all not really important for "my case" but in general it looks a bit like a shortcut.

I still think about an alternative way for me. It's all too complicated.

Imagine an asynchronic connection to the server. The server does not have any leases, callbacks etc. It does not lock on its end because I don't want to have it changed by anything else.

All what it has to do is supplying data, as from a local disk, and return "data written".

So, a journal written for another filesystem, e.g. ext4, could be used to provide the local cache of changes.

Is there a "generic" journal which could be used for this?

Would it be feasible to implement such a network filesystem? Why doesn't it exist? Or does it?

Regards

Peter