David always loves a reach around. In fact, this site is full of guys, mostly 
white, who love agreeing with each other. Because they don’t want to hurt 
someone’s feelings for fear that person might be their next employer or 
reference. It’s like a cult. Lots of companies promise and deliver 5 9’s. 
Because to not provide it can cost them millions of dollars and lots of bad 
press/lost customers.


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On Monday, August 28, 2023, 8:36 PM, David Crayford <dcrayf...@gmail.com> wrote:

> On 29 Aug 2023, at 8:18 am, Gibney, Dave 
> <000003b5261cfd78-dmarc-requ...@listserv.ua.edu> wrote:
> 
>  Yes, IBM z hardware and z/OS properly sysplexed can achieve many 9s of 
>reliability.  I don't think this is in dispute. 
> But, computers are tools that perform useful things for people. It should be 
> clear that actual availability of application function at the outside 
> endpoints is not nearly as many 9s.
>  It's fairly clear that even IBM support sites don't run solely on Sysplexed 
>zHardware under z/OS achieving lot's of 9s.

Nicely articulated. No matter how reliable your servers are if your network 
provider only offers a 99.99% SLA then your applications are not 99.999% 
available. 

IBM zCloud, which runs all the redundancy,  only offers a 99.99% SLA which is 
perfectly reasonable and actually very good 
https://www.ibm.com/downloads/cas/2DALN6RJ.

It’s become fashionable for network service providers to offer 100% 
availability SLA’s but as usual, the devil is in the detail. If you read the 
small print it’s quite clear that it’s not worth very much other than marking 
material for the provider. 

https://business.bt.com/content/dam/bt/business/v2/PDF/broadband-internet/btnet_sla.pdf

>  I suspect a few LPARs in Sysplex over a couple CECs running nothing but z/OS 
>would never need to come fully down. An expensive POC, but also pretty useless.
> 
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