IBM first introduced Logical Partitioning on iSeries with Version 4 and 8xx hardware. A Primary partition was created, and all secondary partitions were dependent on it. If an IPL, or even a full system save, was done of the Primary, all Secondary partitions needed to be shut down. To minimize this disruption, the concept of a ‘thin Primary’ came about. This was more of a ‘management’ partition, having only the minimum operating system components required to support the Secondary partitions. As such, it rarely needed to be shut down.
With Power5 hardware and the HMC, the concept of Primary and Secondary disappeared. Each partition was independent of the other. However, configuring separate physical partitions could become expensive, especially for those customers with smaller disk capacity needs.
Version 7 introduced ‘i hosting i’ on Power6 and newer hardware. This offers users a great deal of flexibility in creating hosted partitions for additional applications, backup, testing, and development. More powerful disk controllers, larger drive capacities, and bigger disk arrays allow the creation of multiple hosted partitions on a single disk subsystem. With virtual disk, the size of the partition is no longer dependent on physical disk units and adding or removing capacity is much simpler.
One downside to ‘i hosting i’ is that it reintroduces the concept of Primary (host) and Secondary (hosted). If the Host partition is shutdown or IPL’ed, all hosted partitions must be shutdown also. This is where the ‘thin Primary’ concept can be used. Similar to VIOS, the Primary (host) ‘owns’ all the disk controllers, and virtual disks are created within the ASP(s). The internal tape and DVD can be shared, but each hosted partition can also be assigned physical resources such as Ethernet, WAN, and external tape.
Pete Mayhew of IT Solutions recently configured a system such as this for a small software development company. The current Logical partitions running on a Power5 machine were less than 200gig in size. Using a Power7+ 4-core system with only internal disk, we created the Primary/host partition and 4 hosted partitions, 2 more than they previously had.
Using CL scripts, they are able to backup development libraries each night across the partitions to the host LTO tape drive. On weekends, all the hosted partitions are shut down and a full save is done of the Primary/host partition. This effectively does a full ‘snapshot’ of each hosted partition storage space allowing for easy recovery if needed.
The new Power8 system with more powerful processors, a high performance internal disk controller, and larger disk array capacity makes this solution an excellent choice for customers needing multiple partitions.
Contact us to see how we can help you consolidate your systems