HP A3550A User Manual - A3661-90001 - Page 154

Table 4-3 Restrictions and Recommendations for Binding Disks into LUNs Group to bind Restrictions and recommendations Any group RAID-5 group RAID-3 group RAID-1 mirrored pair RAID-1/0 group Global hot spare Only unbound (UNB) disk modules can be bound. If you attempt to bind a module that is binding (BIN), Grid Manager displays an error message. All disk modules in a group must be of the same type and same capacity to use the modules' storage space fully. You can determine the capacity of a disk module using Grid Manager by selecting that module in the Presentation screen and pressing RETURN. A minimum of three and a maximum of 16 disk modules must be bound. However, for more efficient use of disk space, it is recommended that five disk modules be bound. Exactly five disk modules must be bound per RAID-3 LUN. Each LUN requires a minimum of 2 MB of SP memory on each SP. For optimum performance, 6 MB of SP memory on each SP is recommended, and only RAID-3 LUNs should be bound in the disk array. An even number of disk modules -- from a minimum of two to a maximum of 16 - must be bound. The disk modules can be selected in any order and each disk module in a pair should be on a separate bus. A minimum of four disk modules and an even number of modules must be bound. Grid Manager pairs modules into mirrored images in the order that they are selected. The first and second modules selected become a pair of mirrored images; the third and fourth modules selected become another mirrored pair; and so on. The first module selected in each pair is the primary image; the second module is the secondary image. Used as a back-up for RAID-5, RAID-3, RAID-1/0 and RAID-1 LUNs. The capacity of a disk module bound as a global hot spare must be at least as great as the capacity of the largest disk module it might replace. The disk modules in slots A0, A3, A4, B0, and C0 cannot be bound as hot spares because they are the database drives that contain the SP microcode. In addition, the disk drives in slots A0, B0, C0, D0, and E0 cannot be bound as global hot spares if cache is installed because they are the cache vault drives. Global hot spares should never be assigned LUN number 0. Global hot spares are assigned a LUN number, but are not recognized as an addressable LUN by the host. Note If binding RAID-3 LUNs, follow the instructions located in the Configuring SP Memory for RAID-3 LUNs section on page 4-28 before binding. 4-18 Creating Logical Disk Units (LUNs)