Sectors and Wastage More File Storage Details CSCI 325 Recap Definitions Sector sector size determined by HDD manufacturer size is almost always 512 bytes commonly 63 sectors per track ID: 441050
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Slide1
Clusters, Sectors, and Wastage
More File Storage Details
CSCI 325Slide2
Recap - DefinitionsSectorsector size determined by HDD manufacturersize is almost always 512 bytescommonly 63 sectors per trackhence, a common track size is 31.5 KBCluster
a group of sectors
the smallest unit of disk space manageable by the Operating System
files use whole clusters
hence, some wastage; hence today's lectureSlide3
Recap -Effect of Cluster SizesNTFS NTFS-5 handles max 264 clustersMax Disk Sizewith 4K clusters = 16 TB
with 64K clusters = 256 TB
FAT32
Max
Disk Size
with 32K clusters = 8TB
with .5K clusters = 2TBSlide4
Common Cluster SizesCluster sizes (sectors per cluster) are always powers of 2.Cluster size is fixed at disk format time.Default cluster sizes for NTFS:
Volume size
Windows NT 4.0
Windows 2000, Windows XP, Windows Server 2003, Windows Vista, and Windows Server 2008
7 MB–512 MB
4 KB
4 KB
512 MB–1 GB
4 KB4 KB1 GB–2 GB 4 KB4 KB2 GB–2 TB 4 KB4 KB2 TB–16 TB Not Supported*4 KB16TB–32 TB Not Supported*8 KB32TB–64 TBNot Supported*16 KB64TB–128 TBNot Supported*32 KB128TB–256 TBNot Supported*64 KB> 256 TBNot SupportedNot Supported
http://support.microsoft.com/kb/140365
FAT 32
Volume size
Windows 2000, yadda yadda
7 MB–16MB
Not supported
16 MB–32 MB
Not supported
32 MB–64 MB
512 bytes
64 MB–128 MB
1 KB
128 MB–256 MB
2 KB
256 MB–8GB
4 KB
8GB–16GB
8 KB
16GB–32GB
16 KB
32GB–2TB
Not supported
> 2TB
Not supported Slide5
Wastage - Example 1File Size = 100,000 bytesCluster Size = 8 sectors 100000 bytes clusters needed = ------------------------------------- 8 sectors/cluster * 512 bytes/sectors
100000B
--------------- = 24.41 clusters =
25 clusters
4096B/cluster
Allocated Space
= 25 clusters * 4096B/cluster =
102400Bytes
not used 2400BPercent Wastage = --------- = ------- = 2.34% allocated 102400BExample Stolen from Dr. Foster's CSCI325 Course NotesSlide6
Wastage - Example 2File Size = 100,000 bytesCluster Size = 1 sector 100000Bclusters needed = ------------ = 195.31 = 196 clusters
512B
/cluster
Allocated Space
= 196 clusters *
512B
/cluster =
100352Bytes 352BPercent Wastage = --------- = 0.35% 100352BSlide7
Wastage - Example 3File Size = 30 bytesCluster Size = 8 sectors 30Bclusters needed = --------------- = 1 cluster
4096B/cluster
Allocated Space
= 1 cluster * 4096B/cluster =
4096Bytes
4066B
Percent Wastage
= -------- =
99.27% 4096BSmall Files in Big Clusters = Lots of Wasted SpaceExample Stolen from Dr. Foster's CSCI325 Course NotesSlide8
Wastage - Example 4File Size = 30 bytesCluster Size = 1 sector 30Bclusters needed = -------------- =
1 cluster
512B/cluster
Allocated Space
= 1 cluster * 512B/cluster =
512Bytes
482B
Percent Wastage
= -------- = 94.14% 512BSlide9
Wastage - Example 5
Size of this PowerPoint file = 92,817 bytes
Cluster Size on my office's
WindowsXP
= 4KB
(8 sectors)
92817B
clusters needed
= --------------- = 22.66 = 23 clusters 4096B/clusterAllocated Space = 23 cluster * 4096B/cluster = 94208Bytes 1391BPercent Wastage = -------- = 1.48% 94208BSee Next PageSlide10
File PropertiesUsage = 90.6KB / 92.0KB = 98.48%Wastage = 100% - 98.48% = 1.52%
Size
Allocated Space