RE: iSeries TCO v NT server farm -- MIDRANGE-L

Yeah, but let's be clear here: "rolling upgrades" means a completely
redundant set of servers.  You can't have, say, five servers and then
one that backs up the other five.  So the concept of redundancy on a
server farm is no different than redundancy on an iSeries... except that
with an iSeries you have many more options:

1. You can have a smaller backup box dedicated only to mission critical
functions that is much cheaper than your primary box, and is used during
outages.  My guess is that maintaining such a system in a Windows
environment is a bit more difficult.

2. You can have an offsite box that you lease from a DR firm for major
outages.  With creative planning, you can conceivably use this box for
planned outages.  I'd love to see the offsite DR system that can handle
20 Windows servers--or 120... and how much that costs.

3. You can partition your machine and use a small partition as the
"backup" box as in option 1.  This is less amenable to unplanned
outages, but works very well for planned maintenance and can be a
cheaper option (although with the price of a 500CPW machine down around
$10K, it's harder for me to justify the cost and complexity of
partitioning).

POINT: A single machine is easier to maintain, upgrade, manage and
failover than a cluster.  A cluster provides no more failover capability
than a single machine; you still need redundant machines, connections,
etc. in order to successfully provide HA.


Also, I don't know as much about Windows, Walden, but the vast majority
of software upgrades for the iSeries can be loaded while the machine is
running, and only a subset of them require so much as an IPL, which is
indeed a wee-hours planned outage thing.  Personally, I doubt there are
a lot of truly 24/7 sites.

Frankly, I see "system unavailable" messages on even supposedly 24/7
sites ("The electronic banking system is unavailable for planned
maintenance") with far more regularity than I have ever seen an iSeries
IPLed.

POINT: iSeries upgrades are less frequent, less intrusive and require
less overall downtime than Windows upgrades.


Joe


> From: Walden H. Leverich
> 
> >Most importantly, business is 24x7.  This application, once live, can
> >probably withstand short downtimes in the wee hours each day, but not
> >much more.
> 
> Rich,
> 
> Sure, the iSeries is stable, but it does go down. Sometimes (granted
> rarely) in an unplanned way, but other times in a planned way, be it
for
> hardware upgrades, OS upgrades, full backups, PTF installs, etc. And
> these planned downtimes are often more than "short downtimes in the
wee
> hours each day."
> 
> So, if you need to be up nearly 24x7, are you planning on buying two
> iSeries?
> 
> Part of the advantage of a cluster is so the application can survive
> "unplanned" outages, but the other advantage is the ability to do
> rolling upgrades where you take a part of the cluster offline and
> upgrade it, but the application continues to run on the other parts.
> 
> Just something to add into the mix.
> 
> -Walden