Planning to Configure a Disk Drive

Review the material discussed in this chapter for each kind of disk drive.

Identify the device driver(s) that must be present in the kernel for the interface and disk device you are installing. You will find the device drivers listed in “Selecting Device Drivers for a Disk Device and Interface”.

Once you have planned your disk configuration, proceed to the section, “Configuring HP-UX for a New Disk Device”.

Performance

Overall system performance depends partly on how your disks are arranged on your system.

To optimize performance, consider the distribution of data on your disks. If possible, use several smaller disks instead of a single larger-capacity disk for all disk needs. Configure a mid-sized disk (for example, 677MB or 1GB) for / and /usr file systems and for any software applications. Use separate disks for user files, database files, and anything else that grows. This allows the system to perform more efficiently by distributing I/O across spindles and shortens the time for file-system integrity check.

Do not exceed HP-recommended guidelines for maximum number of disks or disk arrays per interface card. Note too that the kind of disk access (random vs. sequential), CPU overhead and total system capacity, cabling distance, disk-array configuration, and block size all affect performance.

Consult your HP sales representative for information on performance expectations, based on your predominant system I/O workload and disk characteristics.

Considerations for Configuring a Disk Array

You must use SAM to configure and manage the HP A3231A and A3232A disk arrays. The configuration utilities for these devices are unavailable using a command-line interface.

If you are configuring any other disk arrays, be sure that you have loaded onto your system the C2400-UTIL fileset containing the disk array configuration tools.

Consult the hardware documentation to find out what degree of data protection is provided by the RAID level in which the disk array is shipped. If you need to modify the RAID level, use the disk array utilities provided.

If you are configuring a disk array with more than one controller, you will be using more than one target address. Be sure you choose a SCSI interface with sufficient bus addresses available.

Do not attempt to use disk space larger than 4GB without apportioning the space with LVM. HP-UX cannot address disk space in excess of 4GB; any remaining disk space would be unusable. Given this maximum-size limitation, hard partitions will work. Similarly, boot, dump, or primary swap cannot be greater than 2GB.

You can use Logical Volume Manager (LVM) to partition disk arrays into logical volumes, manage mirrored file systems, and deal with file systems on disk arrays in independent mode. See Managing Systems and Workgroups for documentation on configuring and managing file systems on LVM.

Take care to terminate all busses. Keep cabling (including internal SCSI cabling) to within recommended bounds.

Considerations for Configuring a CD-ROM Drive

CD-ROM drives are configured like a standard disk using SAM or command-line interface, but because CD-ROMs hold read-only file systems,

You cannot use a CD-ROM for swap space.
Users cannot create a new file system on a CD-ROM disk.

Considerations for Configuring a Floppy Disk Drive

Floppy disk drives are installed as internal devices on some HP-UX systems. You might need to configure the device drivers into the system for HP-UX to be able to communicate with the media. (See floppy(7) in the HP-UX Reference and “Floppy Disk Drive Configuration Guidelines” later in this chapter for device driver information.)

Floppy disks are not supported as boot disks.
If using SAM, choose the action, Add -> Not Using LVM. LVM functionality is not supported on floppy disks.
Unlike HP hard disks, which are typically initialized before shipping, you must initialize floppy-disk media, using the mediainit command. See mediainit(1M) in the HP-UX Reference for information.
Do not use low-density floppy disks. Supported disk formats vary by system model and are documented on the floppy(7) manpage.
Floppy drives are supported on HP-UX primarily for transferring raw data. Thus, commands such as tar can be used effectively with floppy disks. You must know in what format your media is written.
In some respects, using a floppy disk drive on an HP-UX system differs significantly from using a floppy disk drive on a personal computer:
- Unlike personal-computer floppies, you can make a file system on an HP-UX floppy disk. Use newfs to create the file system. Consult /etc/disktab to choose an entry (for example, ibm1440) appropriate for the capacity of the floppy disk.
  To access a file system on a floppy disk, you must mount it first.
- Media removal and replacement while the device is open is not supported. A floppy disk containing a mounted file system must not be removed prior to being unmounted. Removal of floppy disks while the device is open is likely to result in file system errors and system crashes.
- If an application requires that you insert and remove media while the program is running, the floppy disk should work properly.

Planning to Configure a Disk Drive

Technical documentation

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Performance

Considerations for Configuring a Disk Array

Considerations for Configuring a CD-ROM Drive

Considerations for Configuring a Floppy Disk Drive