Re: [Xen-users] iSCSI Volumes and Xen

[Simon Hobson <linux@xxxxxxxxxxxxxxxx>]

Joseph Coleman wrote:

> I am moving away from NFS due to performance issues and going to 
> iSCSI I have a 4 node environment that I am going to cluster. 
> However, when I share out the iSCSI volume with all 4 servers and 
> mount the volume as /var/vm  on the servers they are unable to view 
> the files or folders the other server creates. How can I get around 
> this?
Step 1 to fixing this is to realise that iSCSI is **NOT** a shared 
file system - ie it will **NOT** replace NFS directly. Mounting a 
volume on more than one system at once without a cluster filesystem 
is absolutely guaranteed to destroy the filesystem as each system 
writes what **it** thinks is the correct data on the virtual disk.
So you have two choices - mount it on one system and share it (eg via 
NFS) to the others, or use a cluster filesystem on all the systems 
that use it.
What may also be a related issue you'd want to consider ...
I, amongst many, have found performance to be dire when mounting the 
iSCSI volume in a DomU - it seems the Dom0 networking just don't work 
well with it. I don't think I'm alone in having had to attach the 
iSCSI volume on Dom0 and share it to the DomU as a virtual block 
device.
--
Simon Hobson

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printer OS on it. If anyone knows where I might get hold of one I'd 
be grateful - requests to Canon drew a blank, it's been out of 
support for years.
Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
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