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CrossBrand - OperatingSystems - Effects of partitioning a drive
Applicable to: United States
Setting up multiple partitions on a drive has several advantages and disadvantages. Multiple partitions allow you to have several drives, and you can use the drives for specific purposes. One partition might be set up for data files and programs that you use at home for job-related activities, while another partition could be set up for personal records and finance programs.
The main drawback to partitioning is that, if the drive goes bad, you've lost all the partitions on the drive. Fortunately, drive crashes are very rare, so this is usually not a problem. Another drawback is that if you have a disk intensive application and all the drives being used are on the same physical drive due to partitioning, the overall performance will be slower than if they were separate physical drives. This doesn't occur often, but knowing this will help you to pick the right size for a drive, as well as determine where to put applications and data files.
You do not need to partition a drive, other than to create a single partition on the drive if you intend to store files on the drive. Since partitioning will destroy the current data on a drive, be sure you have a complete backup before changing the partitions.
The best time, therefore, to run FDISK to create partitions on a new drive is before you put any files onto that drive. The information below can be used as a guideline for determining the sizes that you want to have.
When you create a file, the operating system will initially allocate a physical area on the drive for the file. This area is called a cluster and it varies in size, depending on the size of the drive. If the initial cluster for the file is not enough to contain the file, the operating system will allocate more clusters for the file as necessary.
The size of a partition determines the size of the clusters allocated for a file. A drive with a size of 128 megabytes (MB) to 256 megabytes will use a 4 kilobyte (KB) cluster size. Drives with sizes of 256 MB to 512 MB will use an 8 KB cluster size, 512 MB to 1024 MB will use a 16 KB cluster size, and 1024 MB (1 gigabyte) and above will use a 32 KB cluster size.
For example, assume that your system came with a 250 megabyte (MB) hard drive. Therefore, the cluster size (sometimes referred to as an allocation unit) is 4 kilobytes (KB). If you create a file that has 142 bytes, it will require one cluster or allocation unit that is 4 KB in size. Only 142 bytes of that cluster will be used for storing data, and the rest of that space is reserved for that file in case more data needs to be added to the file.
If you create a file that has 3968 bytes in it, it will take up 4 KB of disk space as well. If you create a file that has 5127 bytes in it, it will take up 8 KB of disk space (the first 4 KB cluster for the first 4 KB of data, and a second 4 KB cluster to hold the remainder).
If you had a 540 MB drive, the cluster size would be 16 KB. Using the above example, the 142 byte file would take up 16 KB of space, as would the 3968 byte file and the 5127 byte file. A little math will tell you that the total of 9237 bytes in those 3 files will take 48k of disk space.
This is the result of the FAT (File Allocation Table) file system architecture, which was devised years ago with DOS 1.0, when the biggest hard drive was 5 megabytes. Since that time, drive sizes have increased, so special adaptations were made around the DOS 3.x time frame to handle larger drives.
The construction of the FAT allows only a finite number of entries in the table, each entry being able to address a single cluster. Thus, to handle the increased space on the newer drives, the cluster size had to be increased. This allowed the FAT table to remain at the same size for compatibility with older programs, while allowing larger hard drives to be handled properly.
Thus, to address more clusters, the number of clusters that could be addressed with one table entry is increased when you move to a larger drive. This allows DOS to work on almost any size drive, at the expense of using up a lot of space if you have a lot of small files that are less than the size of a cluster.
With that in mind, you can now approach the subject of how large each partition should be. The size of a partition should be based on the types of files on the system. In modern systems, a 4 KB cluster size is reasonably efficient for just about anything, and an 8 KB cluster size is somewhat less efficient but still very reasonable. When you get to a 16 KB cluster size (which you would have with a drive capacity greater than 512 MB), then it can start to become a burden, especially if you total up the sizes of all the files on that drive and find that the sum is significantly less than the amount of space that is required to hold the files. If you had a lot of small files that were less than 4 KB in size, you'd have at least 12 KB of unused space for each one.
Therefore, use the following chart (as indicated earlier) to determine how best to set up the drive:
128 MB - 256 MB 4 KB clusters
256 MB - 512 MB 8 KB clusters
512 MB - 1024 MB 16 KB clusters
1024 MB - 2048 MB 32KB clusters
Determine the types of files to be used on the drives, and then set up the partitioning to be used. If you have large databases, use a larger drive size for best efficiency. If you have many text files and other small files (less than 4 KB), use a smaller drive size. In a typical system, you may have a mix of large and small files, so it may require that you determine the size of the partition needed to hold the range of files and then use that partition size with its default cluster size.
Realistically, most drives can probably be set up as 250 MB partitions or 500 MB partitions. This gives you both sufficient space with relatively little unused space per file. If a larger partition is needed, then use it. While an optimum drive size might be desirable, the first consideration must be that all necessary files be able to fit on the drive. In general, the physical drive that is included in the system that you purchase is set up as a single logical partition, which is probably the best method for it. For additional drives that you install, however, setting up multiple partitions may be worth investigating.
NOTE: Any partitioning done will effect the drive letter of Tape Drives, CD-ROM Drives, and Removable Drives.
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Hint Category |
Hard Drives, DOS/Windows 3.x, Windows 95, OS/2 | |
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Date Created |
27-03-97 | |
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Last Updated |
15-03-99 | |
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Revision Date |
15-03-2000 | |
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Brand |
IBM Aptiva | |
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Product Family |
Aptiva, PS/1 | |
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Machine Type |
2011, 2134, 2159, 2168, 2176, 2121, 2133, 2155 | |
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Model |
6R6; C21; C31; C32; 6R9; C31; F31; C6D; 8R6; 8R9; 9R4; 6R8; 7R1; 7R3; 7R6; 7R7; 7R9; 7RO; 8R1; 8R8; 9R2; 9R3; C23; C33; C35; C55; C56; C65; C66; C67; C6V; C6Y; C6Z; C73; C76; C77; F23; F33; F35; F67; 5R5; M91; 2R5; 2R7; 2R8; M30; M35; M50; 2R6; 4R7; 4R8; M40; M54; M58; 3R0; 3R8; M60; M70; 3R4; 3R6; 4R1; 4R9; M31; M51; M52; M63; 2R9; 3R1; 3R3; 3R5; 3R7; 3R9; 4R0; 4R2; 4R3; M41; M53; M55; M56; M57; M61; M62; M71; M72; 5R1; 6R3; A10; A12; A14; 5R2; 5R3; 5R6; 5R8; 5R9; 6R0; 6R4; 6R5; A15; A40; A44; A45; A50; A51; A52; A90; A92; A94; 1R2; 66P; 67P; 86P; OR8; 1R1; 1R3; 1R5; 22P; 24P; 25P; 27P; 29P; 63P; 67P; 82P; 83P; OR6; OR7; OR9; 1R0; 1R1; 26P; 62P; 2R0; P30; C01; C34; M01; NEA; T35; U35; A62; A82; A94; B82; C42; C92; G42; M82; S92; 081; 087; 131; 137; K37; N31; N81; 11E; 13T; 14C; 16E; 17A; 18A; 18T; 19C; 21C; 23C; 28A; 46M; 51D; D50; G11; G13; G43; G46; G46; G49; G49; G50; G53; M40; M40; M46; M46; P11; P13; P43; P50; P53; R04; R05; R06; R09; R38; R42; R43; R44; R84; R86; R87; RO3; S11; S13; S43; S45; S45; S47; S47; S48; S48; S50; S53; W11; W13; W42; W42; W43; W45; W45; W50; W53; 20E; 22T; 24C; 24M; 28V; 39E; 41T; 43C; 45V; 48E; 50T; 52C; 55V; 72E; 74T; 76C; 78C; 79C; 81A; 82E; 84T; 86C; 87C; CC1; D53; G14; G44; G52; G54; G72; G76; G78; G82; NM1; P14; P44; P57; P71; P74; P76; P78; P84; R14; R15; R16; R17; R18; R51; R52; R57; R58; R62; R63; R67; R71; R89; R93; R96; R97; S14; S44; S50; S54; S70; S75; S76; S78; S80; W14; W44; W48; W54; W67; W76; W77; W78; Z33; 28V; 31E; 33T; 37C; 38C; 51E; 54T; 56C; 57C; 88V; BB1; G57; G87; OR1; OR3; OR4; OR5; P89; R28; R29; R31; R74; R78; R82; R98; S55; S85; SR1; US1; W52; W82; S64; S66; S74; S7H; S78; 13R; 14R; 15R; 16R; 19R; 20R; 2R3; S15 | |
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