The Drive Way - Partitions and Volumes, HBAs and RAID
(Page 4 of 10 )
You have a few choices of setup applications that will help you when you’re setting up a new hard drive. Although these choices are described in detail in Chapter 9, a brief mention of them is appropriate here. New name-brand hard drives include setup applications such as EZ Drive for Western Digital or Max Blast Plus from Maxtor (available as a free download at their respective web sites). Both still require aWindows boot floppy disk for formatting the drive for usability. The second and older choice is to use MS-DOS, which includes the applications FDISK for partitioning and FORMAT to format (more details on using MS-DOS are provided in Chapters 9 and 10).
Host Bus Adapters (HBAs)
There are two ATA hard drives (one master and one slave), connected to the only channel available for hard drives on most ATA motherboards, with the assigned master drive at the top, the assigned slave below, and the longer extension of cable leading to the motherboard (see Figure 6-3). The secondary channel is typically dedicated to removable media devices, such as CD-ROM, tape backup, or Zip drives. I’ve offered a scenario in which two CD/DVD drives are used: one as a simple read-only device and the other as a CD-RW, to back up CDs or files on external media. This fills the capacity of the typical ATA motherboard. For any additional devices, such as the optional tape backup drive, you would need to find another alternative, and that’s where expansion controller cards come into play.
Figure 6-3 -- The longer extension of the ATA cable is connected to the motherboard.
RAID
RAID stands for redundant array of independent (or inexpensive) disks and has nothing to do with killing bugs. There are many versions of RAID, used to improve performance, provide failsafe mechanisms, and reduce MTBF. If one disk fails, the redundantly stored data is accessed elsewhere, without any downtime.
A series of RAID hard drives may appear as a single logical hard disk
to the operating system, but it may be a logical drive made up of parts, or stripes, from multiple discs. These stripes may be random bits and bytes of information, but the OS calls them in the order requested.
RAID first appeared around 1988 at the University of California at
Berkeley in papers that defined several data protection and mapping
models for disk arrays. These include striping with parity and mirroring, which duplicates data (such as an NOS) on multiple discs for redundancy, speed, and maximum uptime. Striping without parity is used specifically for speed. Although there are many categories of RAID, RAID 0 through RAID 5 tend to be the most popular.
Some RAID highlights are:
- RAID 0 -- Offers striping without parity for added performance,
but no reliability or redundancy.
- RAID 1 -- Introduced mirroring/duplexing, which are for
redundancy. Mirroring is slower than duplexing, which uses
two controllers for added speed.
- RAID 5 -- Introduced striping with parity, which is fast and
redundant but requires three or more drives and one disk
for parity. Its only drawback is the cost of having one more
extra drive.
- RAID 10 -- Combines mirroring with striping, or RAID 0
and RAID 1.
HBA controller cards essentially add more channels to your system. They can be used for additional ATA hard drives, tape backup drives, RAID, or even SCSI drives. These controller cards range in cost, depending on what you need. For example, an expansion ATA controller card sells for about $30 to $50. I have a PCI Promise ATA66 and another ATA100 (see Figure 6-4), which offer me channels for up to four more IDE devices. My PCI SCSI Tekrom HBA gives me channels for up to 16 total SCSI devices.
Figure 6-4 -- The Promise ATA100 host adapter adds up to four more ATA devices to your server.
Of course, most ATX cases have space for only a few hard drives, usually underneath the floppy disk drive compartment, so you’d need to add any additional drive securely within the upper 5¼-inch drive bays. If you need more than four hard drives, you may consider moving to a full server tower (refer to Chapter 1), which gives you more bays. However, keep in mind that the more hardware you add, the more power you may need. A 300-watt power supply would be sufficient for up to seven devices, if you’re not using any power-hungry AGP or SCSI card, in addition to an IDE HBA controller.
 This chapter is from Build Your Own Server, by Tony Caputo (McGraw-Hill/Osborne, 2004, ISBN: 0072227281). Check it out at your favorite bookstore today. Buy this book now. |
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