LPAR minimum requirements Each LPAR must have a set of resources available. The minimum resources that are needed are the following: - At least one processor per partition.
- At least 256 MB of main memory.
- At least one disk to store the operating system (for AIX, the rootvg).
- At least one disk adapter or integrated adapter to access the disk.
- At least one LAN adapter per partition to connect to the HMC.
- A partition must have an installation method, such as NIM and a means of running diagnostics, such as network diagnostics.
Hardware guidelines for LPARThe pSeries systems that support LPAR have some general guidelines and limitations that should be considered when planning for LPAR, which will be discussed in the following. Processor There are no special considerations for processors. Each LPAR needs at least one processor. Memory When a machine is in full system partition mode (no LPARs), all of the memory is dedicated to AIX 5L. When a machine is in LPAR mode, some of the memory used by AIX is relocated outside the AIX-defined memory range. In the case of a single small partition (256 MB), the first 256 MB of memory will be allocated to the hypervisor, 256 MB is allocated to translation control entries (TCEs) and to hypervisor per partition page tables, and 256 MB for the first page table for the first partition. TCE memory is used to translate the I/O addresses to system memory addresses. Additional small page tables for additional small partitions will fit in the page table block. Therefore, the memory allocated independently of AIX to create a single 256 MB partition is 768 MB (0.75 GB). With the previous memory statements in mind, LPAR requires at least 2 GB of memory for two or more LPARs. The following rules apply only for partitions with AIX 5L or Linux (if available): - The minimum memory for an LPAR is 256 MB. Additional memory can be configured in increments of 256 MB.
- The memory consumed outside AIX is from 0.75 GB up to 2 GB, depending on the amount of memory and the number of LPARs.
- For AIX 5L Version 5.1, the number of LPARs larger than 16 GB is limited to two in a system with 64 GB of installed memory, because of the memory alignment in AIX 5L Version 5.1.
LPARs that are larger than 16 GB are aligned on a 16 GB boundary. Because the hypervisor memory resides on the lower end of the memory and TCE resides on the upper end of the memory, there are only two 16 GB boundaries available.
The organization of the memory must also be taken into account. Every processor card has its dedicated memory range. Processor card 1 has the range 0-16 GB, processor card 2 has the range 16-32 GB, processor card 3 has the range 32-48, and processor card 4 has the range 48-64 GB. If a processor card is not equipped with the maximum possible memory, there will be holes and the necessary 16 GB contiguous memory will not be present in the system. For example, in a system with three processor cards and 36 GB of memory, the memory is distributed into the ranges 0-12, 16-28, and 32-50. In this configuration, the only available 16 GB boundary (at 16 GB) has only 12 GB of memory, which is too small for a partition with more than 16 GB of memory and AIX 5L Version 5.1. - With AIX 5L Version 5.2, there are no predefined limits concerning partitions larger than 16 GB, but the total amount of memory and hypervisor requirements remains a practical limit.
Note: To create LPARs running AIX 5L Version 5.2 or Linux larger than 16 GB, the checkbox Small Real Mode Address Regionmust be checked (on the HMC, LPAR Profile, Memory Options dialog). Do not select this box if you are running AIX 5L Version 5.1.I/O The I/O devices are assigned on a slot level to the LPARs, meaning an adapter installed in a specific slot can only be assigned to one LPAR. If an adapter has multiple devices, such as the 4-port Ethernet adapter or the Dual Ultra3 SCSI adapter, all devices are automatically assigned to one LPAR and cannot be shared. The internal devices can also be assigned to LPARs, but in this case the internal connections must be taken into account. Devices connected to an internal SCSI controller must be treated as a group, as well as devices that contain an IDE device that shares the same PCI bridge. The internal disks, the media bays, and the external SCSI port of systems with internal disks are all driven by one SCSI chip on the I/O backplane. This chip is connected to one of the PCI-X-to-PCI-X bridges, which in terms of LPAR is equal to a slot. Therefore, in a standard configuration, all SCSI resources in the disk and media bays, including external disks that are connected to the external SCSI port, must be assigned together to the same LPAR. There is no requirement to assign them to a particular LPAR; in fact, they can remain unassigned if the LPAR minimum requirements are obtained using devices attached to a SCSI adapter in the CEC or I/O drawer. This can result in complications when an LPAR with the internal SCSI resources is active and a second LPAR needs to be installed using the internal media devices. In a standard configuration, this is not possible without shutting down the active LPAR that contains all the internal SCSI devices. In this scenario, when the second LPAR is installed using all the internal SCSI devices, you must be careful to not override the disks of the first LPAR. To avoid this problem, the best solution for providing access to CD-ROMs and DVD-RAMs for different LPARs is probably to use an external attached DVD-RAM (FC 7210 Model 025) with a storage device enclosure (FC 7212 Model 102). This external DVD-RAM could be connected to a PCI SCSI adapter (FC 6203), which makes it easy to move the DVD-RAM between different LPARs. This solution also provides the advantages of sharing this DVD-RAM between several servers by attaching it to SCSI adapters in different servers. Every LPAR needs its disks for the operating system. Systems with internal disks are connected to the internal SCSI port. As described previously, all SCSI devices, including all internal disks, could only be assigned to the same LPAR. Therefore, for additional LPARs, external disk space is necessary, which can be accomplished by using external disk subsystems. The external disk space must be attached with a separate adapter for each LPAR by using SCSI, SSA, or Fibre Channel adapters, depending on the subsystem. The internal serial ports, diskette drive, keyboard, and mouse are connected to an ISA bus that is in the end connected to the RIO to PCI-X host bridge. Therefore, these ports and the diskette drive could only be assigned together to one LPAR, but these resources are independent of the SCSI resources. The number of RIO cards installed has no affect on the number of LPARs supported other than the limitations related to the total number of I/O drawers supported, and the ability to meet the LPAR minimum requirements in a particular configuration. There are limits to dynamic LPAR. The ISA I/O resources can neither be added nor removed using dynamic LPAR, including any devices sharing the same PCI-X bridge, such as serial ports, native keyboard and mouse ports, and the diskette drive. Not all resources can be removed using dynamic LPAR; for example, you cannot go below the minimum configuration for processors, memory, or I/O (for example, removing a resource such as the rootvg, paging disks, or other critical resources). |