Partitioning Choices


You've planned the services to run on your Mac OS X Server and chosen the hardware on which the server will reside. It's now time to decide if you wish to partition the disk.

Partitioning your disk allows you to easily reformat one partition while keeping software or data on the other. However, partitioning may waste valuable disk space and be less secure, depending on the way the partitions are formatted. You might want to partition a disk to separate the data from the operating system. Or, you might wish to have three partitions: one containing the operating system, one containing the data, and one to back up the data or the operating system. There is no right or wrong way to proceed when you're dealing with partitions. However, with respect to Mac OS X Server, you undoubtedly know the value of backing up your data to another physical location; so, having a local partition for backup isn't likely to be useful.

You have the option of partitioning the disk whether you're installing Mac OS X Server on a Mac with a single disk or multiple disks, such as a RAID array. For example, you may have an Xserve RAID or an Xserve that supports hardware RAID (the G5 Xserve has an option to support hardware RAID via an optional internal hardware RAID card).

Tips

  • Remember, partitioning a disk erases all the data on that disk!

  • It isn't necessary to create several partitions from your disk. Many people run their server software on a nonpartitioned disk.


Clarifying Some Terms

Now is a good time to look at some terminology to ensure that you understand this book's geek-speak (Table 1.3).

Table 1.3. Computer Terminology Regarding Disks

TERM

MEANING

EXAMPLES

Storage device

Any item connected to your Macintosh that can store information. Storage devices may have the ability to be partitioned.

FireWire hard disk, iPod, USB hard disk, Flash cards, USB storage device, PC storage cards.

Drive

A storage device that's physically connected to the computer and that has or can read from spinning platters or disks.

Hard disk drive, CD-ROM drive, SuperDrive.

Disk

A storage device or the part of a storage device that actually stores data. Sometimes used to describe a partition.

CD-ROM disk, hard disk, or external disk, such as a Zip disk.

Volume

A logical section of a disk that can store files.
Volumes are always partitions, even if a disk contains only one partition.

If a hard disk is partitioned into three volumes, each volume appears as a separate icon on the desktop.

Media

Items that store information and that generally are disposable and plentiful.

CD-Rs, CD-RWs, DVD-Rs, DVD-RAMs, floppy disks, Zip disks.

RAID

Redundant Array of Independent Disks. Makes several drives act and look like a single drive. Levels of RAID exist.

Since RAID arrays are multiple disks, examples generally involve additional internal hard disks or preconfigured external RAID systems such as Xserve RAID from Apple.



RAID Review

RAID stands for Redundant Array of Independent Disks. The concept is easy to understand: Take two disks, make the operating system think they're one disk, and you can perform digital magic.

For example, if the operating system thinks it has one big disk, you can have the RAID software write the same information to both disks. The reason to do this is clear: redundancy of data (fault tolerance). If disk one fails, disk two has the identical data. This is known as RAID level 1. Table 1.4 describes the RAID levels.

Table 1.4. RAID Levels and Their Uses

RAID NUMBER

RAID NAME

IMPLEMENTATION

ADVANTAGES

DISADVANTAGES

0

Striping

Writes small amounts of data to each drive, switching back and forth

Speed

No gain in disk space
If one disk dies, all data is lost (no fault tolerance)

1

Mirroring

Writes identical data to both drives

Fault tolerance
Hot swapping of disks, if supported

No gain in disk space

3

Striping with parity

Writes to each disk, and writes a parity check to a separate disk

Speed

Usually involves a move to hardware RAID

0+1

Mirrored striping

Two sets of striped arrays

Speed
Fault tolerance

Somewhat expensive

5

Distributed parity

Writes data to each disk; parity is written across the disks

Extremely fast read rates Fault tolerance

Somewhat slower writes
Three-disk minimum to implement

10

Mirroring

Mirrored array is striped across two RAID controllers

RAID level 1 advantages over two controllers

Four-disk minimum to implement

30

Striping with parity

Parity and striping across two controllers

RAID level 3 advantages over two controllers

Six-disk minimum to implement

50

Distributed parity with striping

Writes data to each disk; parity is written across disks across two controllers

RAID level 5 advantages over two controllers

Six-disk minimum to implement


RAID systems must have at least two disks but can have several, based on the configuration and your budget. RAID can be software based or hardware based; hardware-based RAID is more versatile.

Apple's support for RAID involves both software and hardware RAID. The Disk Utility application can do software RAID on disks, and hardware RAID is supported by Apple's Xserve and Xserve RAID. The G5 Xserve can hold 3 disks, the G4 Xserve can hold 4; the Xserve RAID can hold up to 14 disks over two controllers and is managed by an application called RAID Admin.


When you're setting up Mac OS X Server for the first time, you'll boot from Install CD 1. Once you've booted off a Mac OS X Server CD, you have access to the disk(s) via Disk Utility on the CD and remotely via ssh (the ssh daemon doesn't run when you boot from a Mac OS X Client CD). You'll likely run Disk Utility and partition the disk(s) in this manner.

To partition a disk:

1.

Boot from the Mac OS X Server Install CD 1.

2.

Choose Installer > Open Disk Utility.

The Disk Utility window appears, showing all mounted volumes in the left pane's disk and volume list.

3.

Select your disk from the disk list menu.

4.

Click the Partition tab (Figure 1.1).

Figure 1.1. Click the Partition tab.


5.

Choose the number of partitions you wish to create from the Volume Scheme pop-up menu.

6.

Click each partition in the map below the pop-up menu, and give it a name, format, and size.

Recall that the minimum size for a Mac OS X Server 10.3 hard disk is 4 GB.

7.

Click the Partition button, and wait for the confirmation dialog. Then click the Partition button in the confirmation dialog (Figure 1.2).

Figure 1.2. Click Partition in the confirmation dialog.


8.

Choose Disk Utility > Quit Disk Utility.

You have now partitioned your disk into individual volumes.



    Mac OS X 10. 3 Server Panther. Visual QuickPro Guide
    Mac OS X Server 10.3 Panther: Visual QuickPro Guide
    ISBN: 0321242521
    EAN: 2147483647
    Year: 2004
    Pages: 105

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