1. IOS110 Introduction to Operating Systems using Windows Session 5 1

2. Objectives: Basic Disks Dynamic Disks File Systems

3. Fault Tolerance – the ability of a system or subsystem to protect itself from failure. Tandem computers 3 Terminology

4. Basic Disks

5. Disk type used on all versions of Windows prior to Win2K Must be used if you wish to dual boot Subdivided into partitions: Primary Partitions Extended Partitions Primary Partition Only Primary Partitions are used by O/S to start the computer O/S looks for first primary partition, marked active Maximum of 4 primary partitions per physical disk (or 3 primary partitions and 1 extend partition) Partitioned using FAT(16) FAT32 or NTFS System Partition – contains files required to boot the PC, e.g. ntldr.exe or boot.ini Boot Partition – contains files found in windows folder Extended Partition Allows physical disk to be configured into more than four logical partitions. Only one Extended Partition per disk permitted Cannot be marked active, however boot partition can be placed there Not formatted as one volume, not automatically assigned a drive letter Divided into segments – each segment holds its own file system Each format segment assigned a drive letter 5 File Systems – Basic Disk

6. Basic Disks Summary of Storage 6 File Systems – Basic Disk Partition Primary Partition Extended Partition Logical Drive Volume Set Stripe Set A section of disk space on one or more disks that has been formatted with a file system. Often functions as a separate entity Section of a physical disk marked for use by an O/S A basic disk partition that can be subdivided into one or more logical drives A sub-partition of an extended partition – format with a file system and assigned a drive letter A combination of partitions on one or more disks formatted a single logical drive Configuration in which data is written or stripped, one block at a time, evenly and sequentially among all disks in the set

7. Basic Disks Summary of Storage 7 File Systems – Basic Disk Mirror Set Stripe Set with Parity Provides fault tolerance by duplicating data from the primary disk to the mirror disk Strip set as above, parity information also provided

8. Dynamic Disks

9. Introduced in Windows2000 Possible to change the configuration of a dynamic disk on the fly without rebooting the system Contains Volumes not Partitions (Basic Disk) A proprietary disk management system – only Win2K and WinXP can access these types of disks Features: Create volumes that span multiple disks, in excess of 2TB. (in basic disk a partition can be no larger than a single physical drive, and no more than 2TB) When extending a partition, the space need not be contiguous. (in basic disk a partition must be created in unallocated space, and it must be contiguous space). Permit creation of spanned and stripped. Basic disks no not support this. Once converted to a Dynamic Disk,the disk cannot be converted back. Disadvantages Not support on portable computers, removable disks, or disks using USB or Firewire Only Win2K and WinXP can access the data Dual boot systems need Basic Disks (regardless of the capabilities of the O/S) 9 File Systems – Dynamic Disk

10. Dynamic Disks Summary of Storage 10 File Systems – Dynamic Disk Volume Simple Volume Spanned Volume Stripped Volume Mirrored Volume RAID-5 Volume Section of disk space (partition) on one or more disks that has been formatted with a file system. Acts a physically separate entity Section of formatted space on a single physical disk that exists by itself and has typically been assigned a drive letter. Multiple volumes on more than one hard disk that are formatted as single logical drive As in Basic Disks. Requires a minimum of two physical disks. As in Basic Disks. Requires a second dynamic physical disk Made up of identical sized areas of formatted disk space located on three or more dynamic disks. Similar to Stripe set with Parity.

11. Simple Volumes No fault tolerance Basic disk partitions are converted to Simple volumes when your convert from Basic Disks to Dynamic Disks Can be extended onto multiple regions (maximum 32) on the same disk- must be formatted NTFS to extend Can be formatted FAT, FAT32 or NTFS Spanned Volumes Consists of separate segments of any size on 2 to 32 different physical disks Main purpose is to access data on more than one hard disk using one drive letter (combine 50MB of free space on one disk with 50MB of free space on another disk for a total of 100MB Data is written to the first member, until full, then to second member until full and so on No fault tolerance More susceptible to failure as failure of any one physical drive will destroy the spanned volume Can be formatted FAT, FAT32 or NTFS Cannot place a boot or system partition on a Spanned Volume 11 File Systems – Dynamic Disk

12. Stripped Volumes Consists of separate segments of equal size on 2 to 32 different physical disks Data read and written evenly across all segments, row by row in 64KB blocks Enables I/O commands to be executed simultaneously – improves performance Provides the best read/write performance of any WinXP disk management scheme No fault tolerance More susceptible to failure as failure of any one physical drive will destroy the striped volume May not include boot or system partitions Can be formatted FAT, FAT32 or NTFS Mirrored Volumes / RAID-5 Volumes Provide fault tolerance Parity information on RAID-5 allows computer to access data Failed volumes should be replaced as soon as possible The O/S will then rebuild the information on the replacement disk WinXP cannot create Mirrored or RAID-5 volumes (must be created on a Win2K or.NET Server), however WinXP can read and write data on these volume types 12 File Systems – Dynamic Disk 64KB Block

13. File Systems

14. Are indexing systems that allow you to save, retrieve, organize and manage data on a disk FAT File Allocation Table Each disk has a File Allocation table containing pointers to segments of information on a disk called a cluster. Each cluster consists of one or more sectors (512B) Three types of FAT systems: FAT12 FAT16 – Very widely used file system. Directory and file information stored in a File Allocation Table that is similar to a database table. Each cluster has an address that is 16 bits in length. T FAT32 FAT12 Oldest Rarely used except with very small partitions. 14 File Systems

15. FAT16 Very widely used file system Directory and file information stored in a File Allocation Table that is similar to a database table Each cluster has an address that is 16 bits in length (2 16 = 65536) If the cluster size is 1KB (2 sectors), then maximum data storage is 64MB) Larger cluster sizes will increase the amount of storage, bust waste space as multiples of whole clusters are assigned to files Do not use FAT16 on partitions larger than 511MB due to the inefficiency of the file system Do not use FAT16 on WinXP unless you are dual booting with an O/S that does not support FAT32 (WinNT < 4.0, Windows95 and older, MS-DOS) FAT32 Released with service pack 2 of Windows95, default file system on Win98 and WinME 32 bit addresses for clusters Cluster sizes at least 4KB in size More efficient than FAT16, less wasted space Minimum size formatted space for FAT32 is 512MB Maximum is 2TB (1 TB = 1024 GB) Used for dual booting an O/S that does not recognize NTFS (Win95 OSR2, Win98, WinME, Linux) Does not support file-level security, compression, encryption, indexing... 15 File Systems

16. VFAT Appeared as part of Windows for Workgroups (Windows 3.11) Services as an interface between applications and the actual file allocation table Support for long file names Can use 32-bit Protected Mode drivers or 16-bit Real-Mode drivers Actual allocation is still 12-bit or 16-bit Preserves disk structures common to original version of FAT Uses 32-bit code for all file access NTFS New Technology File System Best suited to volumes of 400 MB or more Only supported in WinXP, Win2K, WinNT4.0+ Cannot be used to format floppy disks, as it requires high overhead (4.5MB – 10MB) Theoretical maximum file / partition size is 256EB (1million TB) Minimum partition size should be 50MB, due to overhead Faster access speed than FAT, with less disk accesses to find a file File-level security – permissions can be assigned uniquely to each file, instead of the traditional directory level security Allows for file compression, while reducing fragmentation File encryption Disk quotas Some specialized operations require NTFS (e.g. Active Directory) 16 File Systems

17. Long File names Originally FAT support 8.3 format file names (8 characters for the name, a dot, and 3 characters for the extension). The extension was used to categorize the file:.txt,.doc,.dat...) VFAT allowed for 255 character file names FAT Long file names: maximum 255 characters including absolute path Must start with a letter or a number, may not contain any of: »“ \ / [ ] : ; | =, ^ * ? Can contain multiple spaces and periods Regard the last characters after the last period as the extension Preserve case, but not case-sensitive (unlike UNIX / Linux) NTFS File names maximum 255 characters May not contain »“ / \ : | * ? Preserve case, but not case-sensitive, unless being used by a POSIX application 17 File Systems

18. Generating 8.3 File names (alias) 8.3 file names are automatically generated by WinXP so that MS-DOS and OS/2 applications can access them Translation Rules take first 6 LFN characters, and use ~# (tilde, number) extension to keep name unique additional files with same first six characters are treated the same, except the ~# is incremented by one for each file On the fifth file (where the first six characters are the same), first 2 characters are kept, the next four characters are randomly generated. Alias and Secondary Directory Entries For each LFN on a FAT file system, the following is stored: alias 1 entry for every 13 characters of the LFN E.g. a 27 character LFN requires 4 entries: 1 for alias + (27 / 13 = 2.07 = 3) = 4 FAT root directory restricted to 512 entries, a 255 character LFN will consume 21 entries 18 File Systems