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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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DISKTAB(5)						      BSD File Formats Manual							DISKTAB(5)

NAME
disktab -- disk description file SYNOPSIS
#include <disktab.h> DESCRIPTION
disktab is a simple database which describes disk geometries and disk partition characteristics. It is used to initialize the disk label on the disk. The format is patterned after the termcap(5) terminal data base. Entries in disktab consist of a number of `:' separated fields. The first entry for each disk gives the names which are known for the disk, separated by `|' characters. The last name given should be a long name fully identifying the disk. The following list indicates the normal values stored for each disk entry. Name Type Description ty str Type of disk (e.g. removable, winchester) dt str Type of controller (e.g. SMD, ESDI, floppy) ns num Number of sectors per track nt num Number of tracks per cylinder nc num Total number of cylinders on the disk sc num Number of sectors per cylinder, ns*nt default su num Number of sectors per unit, sc*nc default se num Sector size in bytes, DEV_BSIZE default sf bool Controller supports bad144-style bad sector forwarding rm num Rotation speed, rpm, 3600 default sk num Sector skew per track, default 0 cs num Sector skew per cylinder, default 0 hs num Headswitch time, usec, default 0 ts num One-cylinder seek time, usec, default 0 il num Sector interleave (n:1), 1 default d[0-4] num Drive-type-dependent parameters bs num Boot block size, default BBSIZE sb num Superblock size, default SBSIZE ba num Block size for partition `a' (bytes) bd num Block size for partition `d' (bytes) be num Block size for partition `e' (bytes) bf num Block size for partition `f' (bytes) bg num Block size for partition `g' (bytes) bh num Block size for partition `h' (bytes) fa num Fragment size for partition `a' (bytes) fd num Fragment size for partition `d' (bytes) fe num Fragment size for partition `e' (bytes) ff num Fragment size for partition `f' (bytes) fg num Fragment size for partition `g' (bytes) fh num Fragment size for partition `h' (bytes) oa num Offset of partition `a' in sectors ob num Offset of partition `b' in sectors oc num Offset of partition `c' in sectors od num Offset of partition `d' in sectors oe num Offset of partition `e' in sectors of num Offset of partition `f' in sectors og num Offset of partition `g' in sectors oh num Offset of partition `h' in sectors pa num Size of partition `a' in sectors pb num Size of partition `b' in sectors pc num Size of partition `c' in sectors pd num Size of partition `d' in sectors pe num Size of partition `e' in sectors pf num Size of partition `f' in sectors pg num Size of partition `g' in sectors ph num Size of partition `h' in sectors ta str Partition type of partition `a' (4.2BSD filesystem, swap, etc) tb str Partition type of partition `b' tc str Partition type of partition `c' td str Partition type of partition `d' te str Partition type of partition `e' tf str Partition type of partition `f' tg str Partition type of partition `g' th str Partition type of partition `h' FILES
/etc/disktab SEE ALSO
getdiskbyname(3), disklabel(5), disklabel(8), newfs(8) HISTORY
The disktab description file appeared in 4.2BSD. BSD
June 5, 1993 BSD
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