Service and Support

Chapter 4: Installing and Troubleshooting Network Storage Devices

 

Objectives:

This chapter discusses the problems you are likely to encounter regarding hard drives. The objectives important to this chapter are on page 4-1:

  1. Describe Basic Hard Disk Principles
  2. Install a SCSI Hard Disk
  3. Install an IDE Hard Disk
  4. Install and Configure a CD as a NetWare Volume
  5. Prepare a Hard Disk for Use
  6. Create a NetWare Storage System
  7. Set Up Disk Mirroring and Duplexing
  8. Troubleshoot Common SCSI and IDE Disk Problems
Concepts:

The chapter begins with a list of general vocabulary terms about computers in general and about storage devices. This list should be used for reference when reading the chapter. Some key terms are noted below:

  • BIOS (Basic Input/Output System)- the part of the operating system that communicates between a computer and other devices. It is often housed on a ROM chip.
  • block: A minimum unit of space used by NetWare on a disk. This is like a cluster, described above.
  • cluster: a cluster is the smallest area on a disk that can be written to. On small hard drives a cluster may be one sector (one piece of one track). On larger hard drives, a cluster may be many sectors unless you are using a more efficient operating system.
  • heads: magnetic devices that read data from and write data to the platters. (Confusingly, some sources refer to the surface of each platter as a head.)
  • platters: surfaces of the round metal disks in a hard drive. They are made of metal (usually aluminum) because they spin much faster than floppy disks (from 3,000 to 10,000 RPMs) and plastic would fall apart at these speeds
  • sector: This word refers to a wedge shaped area on the disk, or the section of a given track in such an area. Think of a globe of the earth, marked with lines of latitude and longitude. Imagine the globe seen from one of the poles. Now, imagine the globe deflated, so it is flat, like a CD. The lines of latitude are like the track markers on a platter, and the lines of longitude are like the sector markers. There are tracks and sectors in both sides of the disk.
  • tracks: concentric circles on a platter where data can be stored

The basic structure of a hard drive is shown in the picture on page 4-4. For an example online that shows similar images, try this link to Seagate's Online Assistant for installing a hard drive. Activate the program in your browser, then move your mouse over the assistant screen to see images of what it is talking about.

Several hard drive interface types are discussed:

  • IDE - Integrated Device Electronics, cost effective because they incorporate controller card hardware on the drive itself. Supports only drives up to 528 MB.
  • EIDE - Enhanced Integrated Device Electronics, an improvement over IDE. Adds:
    • support for disks greater than 528 MB
    • data transfer rates of up to 16.6 MB per second
    • support of up to four devices
    • support for peripherals other than hard disks
  • SCSI- Small Computer Systems Interface, allows the machine to use one SCSI controller card to daisy chain up to seven SCSI devices (making 8 devices in the chain, counting the card). Supports data transfer up to 5 MBps.
  • SCSI II - two varieties: Fast SCSI II handles up to 20 MBps, Wide SCSI II uses a 16 or 32 bit cable (instead of 8 bit)
  • SCSI III - an improved standard that increases speed (up to 40 MBps) on a 32 bit bus, and the number of devices (up to 31 devices) in the daisy chain. Also called Ultra SCSI.

General troubleshooting tips about hard drives:

  • They are delicate. Transport carefully in protective packages.
  • SCSI problems are usually due to bad IDs (some devices must use a particular number) or bad termination
  • Adding a second disk to a controller can be cost effective, but will slow performance.
  • Some older 386 machines will not support SCSI, and may need ESDI drives.
  • SCSI controllers often have to poll their devices during POST, causing a longer boot.
  • Be careful routing cables. (Especially SCSI cables.) Avoid rolling them, running alongside metal, and running near electrical noise sources like power supplies.
  • SCSI disks are often shipped with PARITY ENABLED. Check whether this is the setting you should use.
  • A Parallel-to-SCSI technology exists, but be aware that it is slower than using a SCSI controller.

The text discusses installing SCSI and IDE drives in detail.

Installing SCSI drives is divided into two sections: physical installation and planning the bus. Physical installation takes place after planning the bus.

SCSI Physical Installation Steps:

  • Plan the bus.
  • Configure and install the Host Bus Adapter if the motherboard has no SCSI support.
  • Configure and install the disk.
  • Attach cables.
  • Set the CMOS type to 0 , SCSI, or "not installed".
  • Complete disk configuration and termination.

Planning the Bus:

  • Termination - Study the diagrams in the book. You will see that in each example you use a terminating resistor in two places:
    • All drives internal to the PC - terminate on the HBA and the last drive
    • All drives in external cabinet - terminate on the HBA and the external cabinet
    • Internal drives and in an external cabinet - terminate on last internal drive and the external cabinet
  • SCSI Addresses - The available addresses are 0 through 7. The HBA usually is assigned 7. In most cases, the lower the number the greater the priority (0 being highest priority) except in MCA systems (God bless IBM...) which reverse the priorities (so 6 is the highest priority device address in MCA).
  • Cabling - Rules for cabling are on page 4-14. Study them.
    • You cannot swap floppy and hard drive control cables. The wiring is different.
    • Pin 1 has a colored stripe on the cable. The HBA should be marked with a 1 or a dot, and the drive should have a notch near Pin 1.
    • 25, 50, 68, and 80 pin cables are all possible.
    • Connectors on SCSI cable must be no more than .5 meters (about 1.5 feet) apart. The maximum length of the cable should be under 6 meters.
    • If using external devices, use impedance matched cables.
    • Be careful routing cables. Avoid rolling them, running alongside metal, and running near electrical noise sources like power supplies.

When configuring the HBA:

  • Set the correct addresses (usually 7 for the HBA).
  • Set termination as noted above (three scenarios).
  • Set standard board settings as necessary: interrupt (IRQ), base memory, I/O address, and/or DMA channel.

When configuring the hard drive, make sure of proper address and termination.

On page 4-20, the text takes up the topic of IDE installation. In an IDE installation, be aware that you can have up to two IDE drives chained to one HBA. If using two drives, the drives will be in a master-slave relationship.

The basic steps for installing an IDE drive, from page 4-20:

  • Configure and install the controller board, if needed. (Note that the text explains that the real controller board is on the hard drive (IDE), but we are referring here to the adapter card or motherboard interface for the drive.)
  • Configure and install the hard drive.
  • Attach cables.
  • Set the CMOS disk type.
  • Complete configuration.

When installing the board, set standard board settings as necessary: interrupt, base memory, I/O address, and/or DMA channel.

Three configurations are possible for the drive:

  • Single drive only - if it is the only drive
  • Master - if you have two and boot from this one.
  • Slave - if you have two and do not boot from this one.

Attaching the IDE cable:

  • You cannot swap floppy and hard drive control cables. The wiring is different.
  • Pin 1 has a colored stripe on the cable. The HBA should be marked with a 1 or a dot, and the drive should have a notch near Pin 1.
  • 40 pin cables must be used. The cable may not be longer than 1.5 feet.

Setting the CMOS disk type for IDE is more involved than with SCSI. You may need to specify only a numbered disk type, or you may have to do a custom configuration (usually, Type 47) specifying number of cylinders, number of heads, storage capacity, number of sectors per track, and write precompensation.

CD-ROMs are discussed next. As storage devices, CD-ROMs are still a more expensive medium as well as being slower than hard drives. A tip on page 4-28 mentions that performance can degrade if a CD-ROM and a hard drive are on the same SCSI controller. On page 4-29 an eight step procedure is given for mounting a CD-ROM as a NetWare volume. Review these steps when studying for certification. Note that the last step is to mount the drive. This is done with a command in NetWare 4.11, but it happens automatically when loading the CDROM.NLM in NetWare 5.

On page 4-32, the text discusses preparing a hard drive for use. Several steps may be necessary:

  • Low-level format - This may destroy an IDE drive. Do not do it unless advised by the manufacturer. It creates the track and sector markers, which must be synchronized with the integrated device electronics. Do NOT do this on an older IDE drive! It was typically done ONCE on IDE drives, at the factory. Doing it again can cause a mismatch with the on-drive electronics.
  • Partitioning - Sets up the logical storage areas on the disk, assigning drive letter pointers, usually using the FDISK utility from DOS.
  • High-level format - Creates the DOS directory system on the drive.

A DOS partition is a logical section of a hard drive allocated for DOS, such as the DOS boot partition on a NetWare server. It is created with the DOS utility called FDISK. This utility is for creating partitions, deleting partitions, making them active and inactive, and making some repairs to disks. FDISK is used to assign Drive Pointers (e.g. C:) to hard drives and partitions on them. It is meant to be menu driven, but some command line methods are also possible. The command "FDISK /MBR", for instance, can create a new master boot record on the disk. As a practical matter, you may want to know that when you create a DOS partition and give it all available space on the hard drive, it is automatically made "ACTIVE". Since you will not do this on a server, (you will only give it about 50MB of space, right?) you have to use a separate step in the FDISK menus to make the partition active (and be able to boot from it).

Page 4-33 illustrates the concept that you will need multiple partitions on some hard drives, notably on servers. Workstations will typically have only one partition on their hard drives, but there are exceptions. If you are still using Windows 3.11, for example, you are limited to about 2GB of usable space per partition. This means you need to partition larger drives as multiple logical devices. (D:, E:, etc.)

Once the logical partitions exist, they can be given a high-level format. This is done only on DOS partitions, and is done with the DOS FORMAT command. You should be aware of the different effects of formatting, listed on page 4-34. Significant effects are:

  • Creating the DOS boot sector.
  • Creating the File Allocation Table.
  • Creating the root directory.
  • Erasing anything already on the partition .

Note that formatting does not automatically place the boot system files on the hard drive. Formatting can do so, if those files are available (if you are running the format command from a floppy disk that has boot files on it) and if you tell it to do so with the /S switch. The syntax of the command is

        format c: /s

To create the IntranetWare partition, you only have to go through the install process for a server. (Workstations do not need this partition.) On page 4-37, the text mentions the Hot Fix Redirection Area, a part of the NetWare partition. This is a place where NetWare can write blocks of data that it intended to write elsewhere, but could not write in the intended area. Two terms are associated with this feature: Redirection Blocks are blocks on the hard drive in where such data is written. Redirected Blocks are actual blocks of data that have been written to this area.

It is good to pause here for a moment and remember the term volume. You should be aware by now that a volume is a unit of storage in the NetWare File System. A volume can be a part of a partition, all of a partition, or may span multiple partitions. We are told that Novell recommends duplexing disks when they are spanned, taking us to the discussion of duplexing and mirroring. This version of the course does not discuss these issues. The chapter discusses these ideas in Objective 7.

Other limitations of IDE disks are listed on pages 4-44. Some of the significant facts are:

  • True multitasking is not supported.
  • Bus mastering is not supported. Bus mastering allows the controller card of the hard drive to take over some tasks from the processor.
  • Older IDE drives had a limit of 528MB capacity.
  • The standard ISADISK.DSK driver may not work. You may have to use the IDE.DSK driver instead. However, this suggestion is only for NetWare versions 3.x and 4.x, as NetWare 5 does not support .DSK drivers.

When mirroring hard drives, both hard drives are controlled by one controller card. When duplexing hard drives, the concept is exactly the same as mirroring, except that there is a unique HBA and a unique controller card for each hard drive. What is written to one is written to the other, but this is more secure (and faster in some cases, such as when using IDE drives). Mirrored IDE disks may not be secure or stable, duplexed IDE disks are more reliable.

RAID (Redundant Array of Independent Disks) may be considered an improvement on mirroring and duplexing. As a generic term, it simply means that two or more hard drives are being used in a system that treats them as one, but is more fault tolerant than other such systems. Some possible benefits to RAID:

  • RAID systems can have faster I/O because they spread reads and writes across the various drives, and do not have to wait for the first drive to move the read/write head after the first pass.
  • RAID systems can store data redundantly, allowing the system to survive the failure of one drive.
  • RAID systems can treat the array as one logical device, which simplifies storage management.

Page 4-60 provides a list of troubleshooting tips that are used in the remainder of the exercises.

SCSI tips
  • Verify that all cables are connected (including the power cable).
  • Verify that all termination is complete.
  • If the disk is your bootable disk, verify that jumpers and BIOS software are set to Enabled.
  • Verify that SCSI IDs are not conflicting.
  • Verify that the SCSI board does not have I/O and interrupt conflicts.
IDE tips
  • Verify that all cables are connected (including the power cable).
  • Verify that the correct BIOS is installed. Older disks require EIDE for additional disks greater than 528 MB.
  • Verify that the ribbon connector on the floppy drive is not backwards.
  • Verify the master/slave configuration. Older disks must be set to single drive only unless you have 2 disks. If you have 2 disks, 1 must be set as master and the other slave.
  • Verify the Pin 1 direction. The colored stripe on the cable should match up with Pin 1 on the drive.