User manual IBM OPEN STORAGE READ ME FIRST 7-9-2010

[. . . ] IBM i Virtualization and Open Storage Read-me First Vess Natchev Cloud | Virtualization | Power Systems IBM Rochester, MN vess@us. ibm. com July 9th, 2010 1 This "read-me first" document provides detailed instructions on using IBM i 6. 1 virtualization and connecting open storage to IBM i. It covers prerequisites, supported hardware and software, planning considerations, install and post-install tasks such as backups. The document also contains links to many additional information sources. Table of Contents 1. IBM i logical partition (LPAR) hosting another IBM i partition 1. 2. [. . . ] To achieve redundancy, adapter-level mirroring in IBM i is used between the two sets of virtualized LUNs from the two hosts. Thus, if a VIOS partition fails or is taken down for maintenance, mirroring will be suspended, but the IBM i client will continue to operate. When the inactive VIOS is either recovered or restarted, mirroring can be resumed in IBM i. Path redundancy to a single set of LUNs Note that the dual-VIOS solution above provides a level of redundancy by attaching two separate sets of open storage LUNs to the same IBM i client through separate VIOS partitions. It is not an MPIO solution that provides redundant paths to a single set of LUNs. There are two MPIO scenarios possible with VIOS that remove the requirement for two sets of LUNs: · · A single VIOS partition using two Fibre Channel adapters to connect to the same set of LUNs Two VIOS partitions providing redundant paths to the same set of LUNs on a single open storage subsystem 9. 3. 2. 1. Path redundancy with a single VIOS If a VIOS LPAR has two or more Fibre Channel adapters assigned and the correct host configuration is created in the open storage subsystem, VIOS will have redundant paths to the LUNs connected to the Fibre Channel adapters. VIOS includes a basic MPIO driver, which has been the default instead of the RDAC (Redundant Disk Array Controller) driver since November 2008. The MPIO driver can be used with any storage subsystem which VIOS supports and is included in a default install. In this case, configuration is required only on the storage subsystem in order to connect a single set of LUNs to both ports on a Fibre Channel adapter owned by VIOS. This multi-path method can be configured in two ways: round-robin, or failover. For storage systems like XIV and DS8000 that support active-active multi-path connections, either method is allowed. Path failover will use one path and leave the other idle until the first path fails, while round-robin will always attempt to use both paths if available to maximize throughput. For 24 systems that only support active-passive connections, such as IBM's DS3000, DS4000, and DS5000 subsystems, failover is the only method allowed. The access method can be configured on a per-LUN basis from the VIOS command line via a Telnet or SSH session. To show the current multi-path algorithm: · lsdev ­dev hdiskX ­attr algorithm To change the multi-path algorithm: · · chdev ­dev hdiskX ­attr algorithm=round_robin, or chdev ­dev hdiskX ­attr algorithm=fail_over These commands must be repeated for each hdisk. Redundant VIOS LPARs with client-side MPIO Beginning with IBM i 6. 1 with Licensed Internal Code (LIC) 6. 1. 1, the IBM i Virtual SCSI (VSCSI) client driver supports MPIO through two or more VIOS partitions to a single set of LUNs (up to a maximum of 8 VIOS partitions). This multi-path configuration allows a VIOS partition to fail or be brought down for service without IBM i losing access to the disk volumes since the other VIOS partition(s) remain active. The following diagram illustrates the new capability for IBM i: 25 Note that as with dual VIOS LPARs and IBM i mirroring, a VSCSI connection from IBM i to both VIOS partitions is required. On the storage subsystem, it is recommended to create a host for each VIOS containing the World-wide Port Names (WWPNs) of all Fibre Channel adapters in that LPAR, and then create a host group comprising those VIOS hosts. A single set of LUNs for IBM i can then be created and mapped to the host group, giving both VIOS LPARs access to the LUNs. Configuring redundant VIOS LPARs with client-side MPIO does not preclude using MPIO within a VIOS for a higher level of resiliency, as described in the previous section. [. . . ] IBM hardware products are manufactured from new parts, or new and serviceable used parts. Any performance data contained in this document was determined in a controlled environment. Actual results may vary significantly and are dependent on many factors including system hardware configuration and software design and configuration. Some measurements quoted in this document may have been made on development-level systems. [. . . ]