Adaptec 2074700-R User Guide - Page 21
Transparency of Host Drives
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Introduction 1.3.6.4 • Single Disks: one disk or a JBOD (just a bunch of drives) • Chaining sets (concatenation of several hard disks) • RAID 0 array drives • RAID 1 array drives, RAID 1 array drives plus a hot fix drive • RAID 4 array drives, RAID 4 array drives plus a hot fix drive • RAID 5 array drives, RAID 5 array drives plus a hot fix drive • RAID 10 array drives, RAID 10 array drives plus a hot fix drive Level 4 On level 4, the firmware forms the host drives. Only these drives can be accessed by the host operating system of the computer. Drives C, D, etc. under MSDOS etc. are always referred to as host drives by the firmware. The same applies to NetWare and UNIX drives. The firmware automatically transforms each newly installed logical drive and array drive into a host drive. This host drive is then assigned a host drive number which is identical to its logical drive or array drive number. The firmware is capable of running several kinds of host drives at the same time. For example, in MSDOS, drive C is a RAID 5 type host drive (consisting of 5 SCSI hard disks), drive D is a single hard disk, and drive E is a CD-ROM communicating with ICP RAID firmware through corelSCSI. On this level the user may split an existing array drive into several host drives. After a capacity expansion of a given array drive the added capacity appears as a new host drive on this level. It can be either used as a separate host drive, or merged with the first host drive of the array drive. Within RAIDCU, each level of hierarchy has its own menu: Level 1 - Configure Physical Devices Level 2 - Configure Logical Drives Level 3 - Configure Array Drives Level 4 - Configure Host Drives Generally, each installation procedure passes through these 4 menus, starting with level 1. Installation includes the initializing the physical drives, configuring the logical drives, configuring the array drives (for example, RAID 0, 1, 4, 5 and 10) and configuring the host drives. 1.4 Transparency of Host Drives The structure of the host drives installed with ICPCON (see Chapter 10, ICP RAID Console) is not known to the operating system. For example, the operating system does not recognize that a given host drive consists of a number of hard disks forming a disk array. To the operating system this host drive simply appears as one single hard disk with the capacity of the disk array. This complete transparency represents the easiest way to operate disk arrays under the operating system. Neither operating system nor the PCI computer need to be involved in the administration of these complex disk array configurations. Software Installation and User's Guide 21