Sams Teach Yourself MCSE Windows NT Server 4 in 14 Days
(Publisher: Macmillan Computer Publishing)
Author(s): David Schaer, et al
ISBN: 0672311283
Publication Date: 12/15/97

5.7.4. Stripe Sets

You use stripe sets to increase disk performance. A stripe set is created from areas of free space on 2 to 32 physical disks. The largest amount of space that can be taken from a single disk in creating the stripe set is equal to the smallest area selected from any disk in the set. If two physical disks contained areas of 100 and 200MB of free space, respectively, the largest stripe set that could be created would be 200MB.

Remember that the exam often tries to test for more than cursory knowledge on a given question. For example, given a disk configuration of three disks, disk 1 with 210MB of free disk space, disk 2 with 410MB of free space, and disk 3 with 600MB of free space, what would be the largest stripe set that could be created?

On the surface it might appear that the largest stripe set that could be created is 630MB by combining the smallest common area between all three disks—210MB from each disk. It is true that you could create a 630MB stripe set by using all three disks, but a stripe set can be created from as few as two physical disks. By using space only from disks 1 and 2 you could create a stripe set of 820MB—410MB from each disk.

Stripe sets cannot be extended. Performance increases are gained by writing 64KB segments of data across the array of disks, one disk at a time. Generally, the more disks used to create the stripe set the better the performance.

Stripe sets are used to enhance disk performance.

Be careful not to confuse stripe sets (RAID0) and stripe sets with parity (RAID5). Stripe sets do not provide fault tolerance; they can be created on both NT workstation and server. Stripe sets with parity provide fault tolerance and can be created on NT server only.

Although the data is written across a series of disks, stripe sets without parity do not provide fault tolerance. If one of the disks used to create the stripe set fails you must restore the data from a tape backup.

5.7.5. Stripe Sets With Parity

Stripe sets with parity not only increase disk performance, but also provide fault tolerance. A stripe set with parity is created from areas of free space on 3 to 32 physical disks. The size of your stripe set with parity is equal to the number of disks times the smallest selected area. Parity information is written on one disk for each stripe. This parity information rotates across the disks.

When reading the exam questions, be sure to note whether the question asks for the size of the stripe set or the amount of usable space. Because parity information takes up one section of each stripe, the total space that is contained in the stripe set is the number of disks times the size of the smallest section. To determine the total space available for data, you must subtract the area that is used for parity. So, if you have the configuration explained earlier, you could create a stripe set with parity of 630MB. However, the amount of space available for data would be (630MB)(630/3) or 420MB.

5.7.6. CD-ROM Drives

CD-ROM drives are read-only devices. The Compact Disc File System (CDFS) is used in conjunction with CD-ROMs. You can change the drive letter assigned to a CD-ROM drive by using the Disk Administrator, and the change takes place immediately.

5.7.7. Saving the Disk Configuration

The Disk Administrator includes an option for saving the disk configuration to a floppy disk. The saved configuration will contain information on drive letters, partitions, volume sets, stripe sets, mirror sets, and stripe sets with parity.

If multiple copies of NT exist on the same machine they will be unaware of how the disk configuration has been modified while the system was booted under a different copy of NT with the exception of drive letter assignments. You can restore the configuration under each copy of NT to update the disk configuration settings. Alternatively, the Disk Administrator can be told to search the system to determine the disk configuration. If multiple copies of NT exist on the same machine determining which is the proper configuration can be difficult.

If the Disk Administrator displays Unknown for any disk areas it is a sign that the configuration might be out of synch.

5.8. Lab

This lab will aid in your learning by testing you on the information presented in this chapter, as well as by giving you exercises to hone your skills. Answers to the review questions can be found in Appendix B, “Answers to Review Questions.”

5.8.1. Review Questions

Question 1

The system administrator of Corporation B is installing NT Server on a x86-based computer with a single hard disk. Which of the following disk configurations can be established on the computer?

A.  Both NT system and boot files can be installed on a single primary partition formatted with NTFS.

B.  The NT system files can be installed on a FAT partition, and the NT boot files can be installed on an NTFS partition.

C.  The administrator can increase disk performance by installing the system files on a stripe set.

D.  The administrator can increase performance by installing the system files on a volume set.

Question 2

The system administrator is planning to load applications to the hard disk of an NT server accessed by DOS-based network clients. Which of the following file systems can be used on the hard disk?

A.  FAT

B.  NTFS

C.  CDFS

D.  HPFS