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Top Forums UNIX for Advanced & Expert Users Physical disk IO size smaller than fragment block filesystem size ? Post 302768713 by rarino2 on Saturday 9th of February 2013 08:56:39 AM
Old 02-09-2013
Sun Physical disk IO size smaller than fragment block filesystem size ?

Hello,
in one default UFS filesystem we have 8K block size (bsize) and 1K fragmentsize (fsize). At this scenary I thought all "FileSytem IO" will be 8K (or greater) but never smaller than the fragment size (1K). If a UFS fragment/blocksize is allwasy several ADJACENTS sectors on disk (in a disk with sector=512B), all "physical disk IO" it will allways, like "Filesystem IO", greater than 1K.

But with dtrace script from DTrace Toolkit (bitesize.d) I can see IOs with 512B size.

¿What is wrong in my assumptions or what is the explanation?

Thank you very much in advance!!

Last edited by rarino2; 02-10-2013 at 08:43 AM..
 

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newfs(8)						      System Manager's Manual							  newfs(8)

Name
       newfs - construct a new file system

Syntax
       /etc/newfs [ -N ] [ -n ] [ -v ] [ mkfs-options ] special disk-type

Description
       The command is a front-end to the program.  The program looks up the type of disk a file system is being created on in the disk description
       file calculates the appropriate parameters to use in calling then builds the file system by forking If the file system is a root partition,
       installs the necessary bootstrap program in the initial 16 sectors of the device.

       If there is no disk description for the specified disk type in the file, the program will use the subroutine to derive disk geometry infor-
       mation from the controlling device driver.  This functionality is provided for MSCP and SCSI disks.

Options
       -N	 Runs in no update mode.  In this mode, will not write to

       -n	 Prevents the bootstrap program from being installed.

       -v	 Instructs to print out its actions, including the parameters passed to

       Options which may be used to override default parameters passed to are:

       -s size	 The size of the file system in sectors.

       -b block-size
		 The block size of the file system in bytes.

       -f frag-size
		 The fragment size of the file system in bytes.

       -t #tracks/cylinder
       -c #cylinders/group
		 The number of cylinders per cylinder group in a file system.  The default value used is 16.

       -m free space %
		 The percentage of space reserved from normal users; the minimum free space threshold.	The default value used is 10%.

       -o optimization
		 Specifies whether the file system will optimize for space or for time.

       -r revolutions/minute
		 The speed of the disk in revolutions per minute (normally 3600).

       -S sector-size
		 The size of a sector in bytes (almost never anything but 512).

       -i number of bytes per inode
		 This specifies the density of inodes in the file system.  The default is to create an inode for each 2048 bytes  of  data  space.
		 If fewer inodes are desired, a larger number should be used; to create more inodes a smaller number should be given.

Files
       For disk geometry and file system partition information

       To actually build the file system

       For boot strapping program

See Also
       disktab(5), fs(5), chpt(8), fsck(8), format(8v), creatediskbyname(3x), mkfs(8), tunefs(8)
       "A Fast File System for UNIX", Supplementary Documents, Volume 3: System Manager

																	  newfs(8)
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