Block devices and block sizes

最新推荐文章于 2025-05-05 17:07:36 发布
原创 最新推荐文章于 2025-05-05 17:07:36 发布 · 764 阅读 · 1 ·
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#byte #linux #disk #ext #c

本文详细解析了硬盘分区的基本概念及其计算方法，并通过具体实例展示了如何计算分区占用的硬盘空间。此外，还介绍了如何利用命令行工具查看硬盘和内存的使用情况。

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       block size是一个笼统的概念，不是一个固定值，在硬盘（一般是512byte），文件系统（分为1kbyte，2kbyte，4kbyte等）及kernel（为1kbyte）中大小不一定

详细可以参考

Block devices and block sizes

block size--file hole


yuebao@yuebao-G31M-ES2C:~$ sudo fdisk -l

Disk /dev/sda: 500.1 GB, 500106780160 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes   //这是指硬盘上1个cylinder（柱面）的大小
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x9d899d89

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       12748   102398278+   7  HPFS/NTFS
/dev/sda2           12749       44618   255995744+   f  W95 Ext'd (LBA)
/dev/sda3           44619       45605     7919616   82  Linux swap / Solaris
/dev/sda4           45605       60802   122070016   83  Linux
/dev/sda5           12749       25496   102398278+   7  HPFS/NTFS
/dev/sda6           25497       44618   153597433+   7  HPFS/NTFS

以sda3  是swap分区的大小，依次为例，此分区占用的大小计算方法，

1.  总共占用的cylinders个数：(60802-45605)=986个

   1个cylinders的大小8225280byte/1024/1024=7.8MB

   占用空间=986x7.8MB=7.5GB

2.直接用Blocks数计算

   1个block size 1024byte，即1k

   则7919616个bloack

  占用空间=7919616x1k=7.5GB

两种方法计算结果是一样的。

另外df是disk free，可以查看硬盘的空间使用情况

yuebao@yuebao-G31M-ES2C:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda4             115G   96G   14G  88% /
none                  2.0G  656K  2.0G   1% /dev
none                  2.0G  7.5M  2.0G   1% /dev/shm
none                  2.0G  356K  2.0G   1% /var/run
none                  2.0G     0  2.0G   0% /var/lock
/dev/sda5              98G   77G   21G  79% /media/d:
/dev/sda6             147G   45G  103G  31% /media/e:

free则是查看内存空间（包括硬盘上的虚拟内存）的使用情况，-m以MB显示大小
yuebao@yuebao-G31M-ES2C:~$ free -m
             total       used       free     shared    buffers     cached
Mem:          3951       3877         74          0        357       1317
-/+ buffers/cache:       2202       1749
Swap:         7733          0       7733




 

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