I want to agree with the comments by Andreas Schmidt, I've got disk
mirroring installed on multiple machines and have not seeing the
problems that Rich Ingram has reported.

There are some caveats though:

1.  Using SYSDIAG, IOMAP on mirrored drives may result in a drive
becoming disabled.  This is a problem that is known to HP, they do not
recommend running IOMAPS.

2.  Mirrored drives must be on different SCSI controllers. And of course
FW-SCSI would be provide the best performance.

3.  If you use FW-SCSI, make sure that the firmware for the controllers
is at the same level.

4.  Make sure that you've got the current patches from HP for mirroring,
the disk drives, and file system.

Mirroring results in twice the number of disk writes (Always), simply
because it must write to two devices.  But the virtual device manager is
smart enough to only perform a read against one device AND it is
supposed to read from the device that has the disk head closest to the
desired block of data. So do a little planning and try to place the
busiest volume sets on different paths. Hint:  buy more FWSCSI cards.

When shutting down the system for patches, planned outages, etc, ALWAYS,
ALWAYS, ALWAYS, (did I emphasize enough), wait for the "SHUT 6"
message.  This is necessary so that a "good housekeeping seal" is
written to the mirrored drives.  If you do not wait, then MPEiX will
choose a drive to be the "standard" and will rebuild the mirrors next
the system is rebooted. Performance will be painfully slow... until the
mirroring has completed the source-to-destination copy activity.


Rick Clark wrote:
>
> I thought I remember a while back an article in one of the HP trade mags
> that described the process of installation and configuration of HP's
> Mirrored/iX. Anyone remember such an article and could they point me to
> where I can find a copy? Thanks in advance. Please reply privately.
>
> Rick Clark
> Senior Systems Analyst
> WW&R
> Cleveland, Ohio