Disk Partitioning

1. Disk Partitioning By: Stefano Polo

2. Overview • Creating divisions on a Hard Disk • Directories and files are then grouped by categories • Data types • Usage • Partitions contains file systems • Space Management • Access Permissions • Directory Searching

3. Overview cont. • A file system can decide how many separate categories of data are needed and the size of each. • Seperating operating system from user files

4. Examples • Partition for Swapping • Keeps frequently used programs and data near each other • Keeping browser cache files in separate partitions keeps them away from each other • Seperating email from audio and photos

5. Benefits • The Use of Multi-booting setups • Having more than 1 operating system • Sharing swap partitions between multiple linux distributions • Allows the need for less memory • Protecting and isolating files • Easy to recover corrupted file systems and operating systems installed • Increase Computer performance • Smaller file systems are more efficient • Higher level of data organization • Keeping videos, photos, audios, emails, etc…seperated

6. PC Bios Partition Types • Used in MS-Dos, Windows, & Linux • Can contain up to 4 Primary or 1-3 primary and 1 extended • Each partition have 16-byte entries in the partition table located in the Master Boot Record • A primary partition contains one file system

7. Primary (Logical) • The "partition type" code for a primary or logical partition can either correspond to a file system contained within (e.g. 0x07 means either an NTFS or an OS/2 HPFS file system) or indicate the partition has a special use (e.g. code 0xBC may mean an Acronis Secure Zone and code 0x82 usually indicates a Linux swap partition). The FAT16 and FAT32 file systems have made use of quite a number of partition type codes over time due to the limits of various DOS and Windows OS versions. Though a Linux operating system may recognize a number of different file systems (ext2, ext3, reiserfs, etc.), they have all consistently used the same partition type code: 0x83 (Linux native). (wikipedia)

8. NTFS • All file data are stored as metadata • Simply just data about data • May describe individual datum, content item, or a collection of data • Allows any sequence of 16-bit values for name encoding • uses B+ trees to index file system data • Master File Table (MFT) contains metadata about every file, directory, and metafile on an NTFS volume

9. File Allocation Table (FAT) • Used mostly today in floppies and solid-state memory cards (flash memory) • Gives convenience towards sharing data between operating systems on one machine • Uses a table which contains information on which areas that belong to files are free or unusable • Table also gives information on where the data is actually stored • To limit the size of the table, disk space is allocated in hardware sectors called clusters • Maximum numbers of clusters have increased over time • the number of bits required to identify a cluster is used to name the successive major versions of the format • Fat12 • Fat16 • Fat32

10. Drawbacks of FAT • When files are deleted and new files are created, directory fragments tend to get scattered over the entire disk • This causes slow read/write processes • Defragmentation can solve this issue • Can be a lengthy process • Would need to be performed reguraly • Solid-State should not be defragmented since they tend to wear down eventually

11. Extended • Secondary to primary partitions • Hard disk may contain 1 extended partition • Can be sub-divided into logical drives • Each are assigned additonal letter drives • Examples • Primary partition would be C: • Extended partition would be E:, G: etc

12. Compressed Disks • Compressed to create additional space • Creating one large file in a partition • Storing the disk’s data in this file • At startup, device drivers open this file and assign it to a separate letter • To avoid confusion, the original partition and the compressed drive had their letters swapped • Compressed disk would be C: • Uncompressed disk were given higher names

13. Partitioning Schemes • Microsoft • create a single active primary partition, the C: drive • Where all system, user data, applications, and page file all reside • Some users, however, prefer to create multiple partitions so that the operating system can be stored separately from other kinds of data.

14. Partitioning Schemes cont. • Unix • creation of separate partitions for /boot, /home, /tmp, /usr, /var, /opt, swap and all remaining files under the "/" (root directory) • Advantages • if one file system gets corrupted, the rest of the data (the other file systems) stay intact, minimizing data loss • can be accessed read-only and the execution of setuid files disabled thus enhancing security • performance may be enhanced due to less disk head travel

15. Partitioning Schemes cont. • Disadvantages of Unix scheme partition • user could run out of hard drive space in his or her /home partition • good implementation requires the user to predict how much space each partition will need, which may be a difficult task • Logical Volume Management, often used in servers, increases flexibility by allowing data in volumes to expand into separate physical disks • Another option is to resize existing partitions when necessary.

16. Partition Recovery • When a partition is deleted, generally only the table entry is removed • The data is still on the hard disk but maybe un-accessible • Specialized recovery tools can access the data and recreate the table entry • Some disk utilities may also overwrite a number of beginning sectors of a partition they delete • In this case it may be possible to restore a FAT32 or NTFS partition if a backup boot sector is available