Re: With SAN should you still use internal disk for vios?

["Larry \"DrFranken\" Bolhuis" <midrange@xxxxxxxxxxxx>]

SAN Casters up? Yep. Know of two of them.

Both Lost everything, causing a total system rebuild. We consultants 
call that: "Profitable."

Both were customer's fault really. One had server and SAN plugged into a 
UPS that after about 5 days had a fight with the server and SAN. Server 
and SAN would see voltage go down, so they raise current. (Ohm's law, 
not Ohm's suggestion!)  UPS would see current go up and push a little 
harder, raising voltage. Server and SAN react accordingly. Eventually 
this went from 'up a little' 'down a little' to swinging more and more 
and eventually the UPS simply shut down hard. Customer then chose to 
leave the entire setup powered off for a week. This let the cache 
batteries in the SAN go flat and therefore all data on all volumes was 
lost.

UPS was huge and easily able to handle the load, even with the server 
and SAN it was under 20% load. Turns out the IBM approved solution was 
to plug in two 1,500 watt heaters to the UPS and turn them on max. Pure 
resistance loads bringing the load up to a point where the voltage 
didn't fluctuate.

Not particularly efficient of course but it worked. (and no, no longer 
in play!)

Second customer had misunderstood power cables from Blade Center and 
didn't have them split correctly between A and B power. When one side 
was taken down for maintenance so did entire blade center. Somehow that 
smoked the SAN as well. Complete rebuild again.

	- DrF

On 8/22/2022 9:27 AM, Rob Berendt wrote:
> Of course with two VIOS lpars (for redundancy) and each running mirrored drives you end up with 4 NVMe drives.  Just to run VIOS.
>
> How much time does it save you to be able to get VIOS running while you are waiting on SAN?  At best it probably keeps you from breathing down the storage guy's neck while you are waiting.
>
> Has anyone on this list actually been in this situation where the SAN went casters up?
>
> I suppose having some device which could 'ping' FC might tell you that it's the switch vs the SAN.
>
>
> Rob Berendt