RE: [Xen-users] Shared SAN disk LUN between 2 servers and migration problem

[Pekka.Panula@xxxxxxxx]

> George Rushby <george@xxxxxxxxxxxxxx> 
> Sent by: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> 
> 16.10.2008 11:50
> 
> To
> 
> "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>
> 
> cc
> 
> Subject
> 
> RE: [Xen-users] Shared SAN disk LUN between 2 servers and migration
problem
> 
> You are connecting to the same volume with at least 2 servers. This
> will cause your files system to eventually corrupt. The array has
no
> knowledge of your operating system at this level you should think
of
> a volume as a disk drive. If you are not using a cluster you must
> restrict access to the volume to only one server. Once you connect
> to the volume you share the volume through the server. Most people
> will set up a server with 2 NIC's one to connect to the iscsi vlan
> setup for the array and the other is on the public vlan. This way
> you separate your traffic and are able to share the data on the volume.
>  
> You should also look in GFS

But why you need GFS if only one server is doing access
to shared LUN at the time. Server 2 is running DomU and its accessing multipath
device there (reading/writing) but on another server its just there waiting,
no server is actually accessing it until server is migrated to there. I
am running only one access per multipathed LUN at the time, not several
nodes to same LUN, i dont need active/passive failover as i just want to
migrate servers when i am doing maintenance, eg. rebooting Dom0 etc. Other
Dom0s do not touch my multipath device at all. Meaning one multipath device
per DomU server. And this is on FC SAN Disk system, so servers are pointed
to same LUN on array but only one server is writing it at same time.

So i am lost here? This does not work, eg. Linux/Xen/multipath
device does not sync all operations to block device when Xen is migrating
server to another server? Why Xen does not say to OS to sync data to disk
when migration is happening, or does it?

Anyway on HVMed Windows 2003 Standard Server i am
getting corruption when i do file access during migration operation, i
have tested this by installing 7-zip compression program and put it to
compress eg. windows -directory and then migrate it to another server and
then back to original and then when verifying compressed file 7-zip says
lots of files are corrupted. Not tested on PV host, but anyway, currently
my need is to run many Windows servers so i need to get this working. Ofc
i can do it now without migration, by manually shutting down DomU and copying
its Xen configuration to another server and starting server there...

Terveisin/Regards,
   Pekka Panula, Net Servant Oy

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