On Saturday, 03/13/2010 at 06:49 EST, Frank Pani <[email protected]>
wrote:

> 1)  Because the database will be 200-300GB, we can use LVM and have it
> available to mount RW on either system.   We need to be very careful not
to
> mount RW at the same time; else we risk destroying the data.  In cases
> where customers are using VMWARE or Xen on distributed, you ensure this
by
> using PaceMaker to tell the hypervisor to issue a STONITH to totally
kill
> the primary machine.  This ensures, that the filesystem will be RW only
on
> the backup now.  However!  There is currently no capability on z/VM to
> allow PaceMaker (or any other software that I know of) to do this.

For quite a while now we have had the System Management API (SMAPI). Write
a program on Linux that uses SMAPI to stop the Linux guest.  Have
PaceMaker execute said program.

> Any thoughts will be appreciated it.   I also saw somebody write about
> putting a NFS up and then use it over hipersockets.  This seems simple,
but
> alas, 800 transactions per second on a NFS system - performance issues
> looming?

Possibly.  HiperSockets are not free.  They are synchronous within the CPU
and can be blocked by a slow target LPAR.  The more transactions you have,
the more MIPS you suck out of the machine.  So you have to have the
headroom within all LPARs and the overall CPU capacity to start using
HiperSockets in a big way.

Alan Altmark
z/VM Development
IBM Endicott

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