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

So yes, it should be enabled by default in RHEL6 (haven't got any RHEL7
boxes to check).

I am afraid the leases are not the same.

I came across leases first when looking for a NFSv3 extention integrated in FreeBSD, NQNFS (not quite NFS).

http://docs.freebsd.org/44doc/papers/nqnfs.html

These leases expire after a short period so have to be renewed regularly to "keep" the file.

In NFSv4 a callback server receives a revocation of the exclusive file access instead.The callback server, nfs4cbd, is needed according to the FreeBSD implementation, and Oracle's (http://docs.oracle.com/cd/E19253-01/816-4555/rfsrefer-140/index.html)

I cannot find any reference on Linux for it, though.

Trent, NFS is called Nightmare File System for a reason. My experience started with crashing Nextstep machines with block sizes of 8192 (when trying to connect them with Solaris machines), and it went downhill from there.

NFSv4 is a step forward, I hope.. I did not touch NFS for ca. 10 years, I think. I did not miss it much;-)

Regards

Peter