[ILUG] HA NFS

[Ronan Mullally]

On Mon, 15 Dec 2008, john Moylan wrote:

> On Server1 I have configured an LVM2 LV on the LUN with an EXT3 flesystem.
>
> On Server2 I have mounted the same LUN as readonly.
>
> I'm exporting NFS4 from both servers as Readonly.
>
> Is there any reason why I should be using CLVM or GFS2 in this sort of
> situation? Instead of plain LVM2 and EXT3?
>
> Everything looks like it's working and I can't see any reason why it
> should not work? Server2 cannot access any files or write any LVM meta
> data to the LUN because it has Read only access.

The above suggests that Server1 has write access to the filesystem. What
happens when Server1 writes something to the filesystem?  Until the data
is actually written to disk you're going to have a window where an NFS
read request to Server1 will return different results to an NFS read
request to Server2.  How large that window is depends on how long the
kernel takes to commit changes in the write cache.


-Ronan