1. Chapter 6: Configuring Server Storage, Backup, and Performance Options

2. Learning Objectives Partition and format hard disks
Explain types of disk partitions
Create volume sets
Extend a disk volume
Implement disk redundancy through striped sets, striped sets with parity, and mirrored sets
continued

3. Learning Objectives Perform disk backups
Develop a tape rotation scheme
Configure server memory to improve performance
Configure Windows NT Server for a UPS

4. Hard Disk Basics Low-level format Tracks
A software process that marks tracks and sectors on a disk
Necessary before a disk can be partitioned and formatted
Tracks
Concentric rings that cover an entire disk
Each ring is divided into sectors in which data are stored

5. Hard Disk Basics Sectors Other nomenclature A portion of a disk track
Disk tracks are divided into equal segments, or sectors
Other nomenclature
tracks also known as “cylinders”
“heads” are number of r/w devices
LBA = logical block address

6. A Disk Divided into Tracks and Sectors
Sectors within a track

7. Disk Partitions
Partitioning: The process of marking a group of tracks and sectors in preparation for a file system
breaks a physical disk into logical volumes
Free space: Disk space not yet partitioned for use by a file or operating system
different from “free space” (i.e. space available to store files) within a volume

8. Disk Partitions
Master boot record (MBR): Data stored in the first sector of a disk, including startup information and information about disk partitions
Partition table
Table containing information about each partition on a disk
Provides information to the computer about how to access the disk

9. Disk Partitions Boot loader Various choices
mini-program, lives in MBR or first sector of partition
presents menu of boot choices to user
generally has timeout and default choice
Various choices
NT boot loader
OS/2 boot manager
Linux “LILO”
generally, independent of the OS

10. Primary and Extended Partitions
Primary partition: Partition or portion of a hard disk that is bootable
Extended partition: Partition that is created from (otherwise) unpartitioned disk space; contains “logical partitions”

11. Entering the Partition Size

12. Partition Types
Active partition: Partition from which a computer boots, or starts
can change active partition to enable booting of other OSs
Boot partition: Partition that holds the Windows NT\Winnt folder containing the system files
boot partition gets special treatment by OS

13. Formatting
Formatting: A process that prepares a hard disk partition for a specific file system
Volume: loosely defined as “an amount of storage”. Can be a partition (any sort), a stripe set, etc. Generally seen by users as a drive letter (ex. D:) no matter what it’s made up of.

14. Formatting
Assigning a drive letter

15. Creating Volume Sets
Volume set: Two or more formatted partitions (volumes) that are combined to look like one volume with a single drive letter
Advantage
Ability to manage several small disk drives more easily or to maximize the use of scattered pockets of disk space across several disks
Disadvantage
If one disk in the volume set fails, the entire volume is inaccessible

16. Extending a Volume
Add (e.g.) another disk until larger disk drives are purchased
increases available space to users
Same risks as volume set
disk failure

17. Implementing Disk Redundancy
Operating system disk protection
Disk striping
Striping with parity
Disk mirroring

18. Operating System Disk Protection
Hot fix: A data recovery method that automatically stores data elsewhere when a damaged area of disk prevents that data from being written
“Hot” because it happens without interruption to the system

19. Operating System Disk Protection
Sector sparing: A fault-tolerance method that reserves certain hard disk sectors so that they can be used when a bad sector is discovered
Cluster remapping: A fault-tolerance technique that flags a damaged cluster and finds an undamaged cluster on which to write data
“cluster” is mostly analogous to a sector

20. Disk Striping
Stripe set: Two or more disks set up so that files are spread in blocks across the disks
Disk Disk Disk Disk Disk 5
Row 1
Row 2
Row 3

21. Disk Striping Advantages Disadvantages Tradeoffs speeds access to data
rotational and seek latencies
spreads out wear & tear
Disadvantages
if one disk fails, can’t re-create data
different options (RAID levels) address this
Tradeoffs
one adapter for all disks, or one each

22. Striping with Parity
Stripe set with parity: Three or more disks in which files are spread across the disks in blocks, and a parity block is written on each disk to enable data recovery should one disk in the set fail
Disk Disk Disk Disk Disk 5
Row 1
Parity block
Parity block
Row 2
Parity block
Row 3

23. Striping with Parity Definition of “parity”
the result of a mathematical function performed on the data, which can be used to reconstruct what the original data were
There must be 3 or more disks to do this
Recall server hardware discussion
hot-swap disks versus power-down, etc.

24. Disk Mirroring
Involves creating a “shadow” copy of data on a backup disk
also “duplexing” - different adapters
Advantages
Most guaranteed form of disk fault tolerance
Well suited for mission-critical data
Disadvantages
Doubles time needed to create or update information

25. Increasing Disk Performance and Longevity
Make sure that one disk is not working harder (e.g. accessed more often) than other disks in a multiple-disk server
Use striping or striping with parity
Relocate files to distribute disk access more evenly
Use defragmenting to reorganize files to reduce the number of empty spaces between files

26. Disk Security Through Backup Techniques
Advantages of local (eg. one per server) tape drive backups
Causes no extra load on network
Can perform backups on a multiple server network even if one tape drive fails
Provides more assurance that the Registry is backed up
Can also back up on other media
Jaz disks, ZIP disks, writable CD-ROMs, etc.
another hard drive (disaster recovery)

27. Disk Security Through Backup Techniques
Full backup: Backs up all volumes, directories, and files
Incremental backup: Backs up only those files that have changed since the previous backup
generally, much smaller than full backup
quicker to perform
less media needed (number of tapes)

28. Backup Options Normal: Same as full file-by-file backup
Copy: Only files or directories selected
Incremental: Only files with archive attribute
Differential: Same as incremental but does not remove archive attribute
Daily: Only files that have been changed/updated on the day of backup

29. Tape Rotation
Helps ensure alternatives in case there is a bad or worn tape
e.g., Tower of Hanoi procedure: Rotates tapes so that some are used more frequently than others
depends on importance of data, budget for tapes, skill and time of backup operator
Consider off-site storage for disaster recovery

30. Configuring a Server to Improve Performance
Configuring virtual memory
Configuring memory to match the user load

31. Configuring Virtual Memory
Virtual memory: Disk space allocated to temporarily hold data when there is not enough free RAM
much slower than RAM (e.g. not a replacement)
Paging: Moving blocks of information from RAM to virtual memory on disk
Page file: Disk space reserved for use when memory requirements exceed available RAM
General rule for sizing = Amount of installed RAM + 12 MB

32. Configuring Virtual Memory
System “swaps out” pages to disk as needed
ex. when multitasking, use RAM for current program, put others on disk temporarily
happens automatically; neither user nor programmer has to do anything
Can dramatically affect performance
sometimes greatly increases contention for the disk containing the pagefile
if misused, system spends all its time copying data and very little doing actual useful work
adding RAM memory (e.g., avoiding VM) is better

33. Configuring Memory to Match the User Load
Server functions
Use RAM and paging
Software applications
Printing
Currently running services
Network connectivity functions
Use RAM only
Number of user connections

34. Configuring Server RAM Hints

35. UPS Fault Tolerance
Uninterruptible power supply (UPS): A device that provides immediate battery power to equipment during a power failure or brownout for a limited time period
Online UPS: Battery backup device that provides power to equipment directly from its batteries at all times
Offline UPS: Battery backup device that waits until there is a power decrease or sag before switching to battery power

36. Chapter Summary
Properly setting up disk storage is as important as selecting it.
Partition disk drives through the Disk Administrator
After partitions are set up and formatted, implement a fault-tolerance method.
Disk striping
Striping with parity
Disk mirroring
continued

37. Chapter Summary Disk performance affected by Fragmentation
Distribution of files across multiple disks
RAM configuration
Virtual memory
continued

38. Chapter Summary
Establish a tape backup method to guard against data loss.
Full and partial backup techniques
Tape rotation
Also, can protect against power outages with a UPS