When you think about it, our first job is to keep our systems up and running. Or at least walking, crawling, even staggering. But keep them up we must. The mail must get through, the system must stay up. We build redundancy at all sorts of levels into our systems because we want to avoid that dreaded disease known as SPOF - the Single Point of Failure.
Outages are expensive
Unscheduled outages bring your computer system to its knees. They can have similar effects on your nervous system. There is the post-mortem where you hope to find the root cause and hope to prove it's not you.
But even scheduled outages - the ones we plan weeks ahead - are costly. There is the planning, begging for permission for the outage, negotiating a time which most suits the users (and most disrupts your family), the co-ordinating of key stakeholders to be on standby at an ungodly hour. Maybe there are fallback plans which need to be in place and then there is that intangible user perception that the system is unstable because they keep having to work around another weekend of downtime.
So before you plan to inconvenience maybe thousands of users by shutting down your server, ask yourself one question:
Do you really want an out?
Even if you get the agreement from the
business that you can have an outage on your Power server, think of
whether having a Hardware Management Console (HMC) as part of your
configuration can help you to reclaim your weekends or sleep time. Here are some ways the HMC allows you to skip several of those outages:
- concurrent firmware updates when you're updating within the same release of system firmware
- firmware updates to several servers
simultaneously - one HMC can do it all
- dual VIO servers - you can upgrade one VIOS at a time without losing your disk or network connectivity
- some hardware
installation and replacement
partition mobility which lets you move a running LPAR to a
of Workload Partitions (WPARs)
On smaller systems, you may not need a dedicated HMC for management. Even so, it is worth thinking about having one anyway, especially when you consider the benefits of not having to schedule system outages for many key tasks. If you don't have an HMC and you use the Integrated Virtualization Manager (IVM), many of the tasks mentioned above will still require an outage. For example, with the IVM, every firmware update is disruptive - it requires a reboot of all LPARs on the system. And if you want dual VIO servers for redundancy, you must have an HMC.
how the two VIO servers can work to prevent unnecessary outages.
Dual VIO servers
On an HMC-managed system, you can set up SEA Failover for the network and even have SEA Failover with VLAN tagging. When VIO Server 1 goes down, traffic can still go through VIO 2. Similarly, you can configure multiple paths to storage, as explained in this excellent presentation by Janel Barfield on Advanced Power6 VIO configurations.
Converting from IVM to HMC
Although there is no official procedure to migrate from IVM to HMC, I have done it successfully for a p6-520 and a p6-550. Rob McNelly has a post on IVM to HMC Migrations. If you're scheduling lots of outages for tasks which could be done during business hours if only you had your systems connected to an HMC, you might find the total savings of avoiding those outages more than justifies the purchase of a single HMC to manage multiple Power systems.