02-17-2013
Hello Praveen,
I'm not sure if you are mixing FS layer and phisical (disk driver) layer. I was speaking about FS layer (and block device driver layer) in my first post.
mcnamara answer was right.
Quote:
Originally Posted by
Praveen_218
A block is still (on most FS) refers to 4K of data only.
On most system the page-cache is still of this fix sizes. Hence on all block I/O is of 4K or less. The file systems on such system utilizes the maximum size which is 4k.
However, if you see the disk architecture, they have been under trial by various vendors with various sector sizes; with 512bytes sector disk supported by most of the File system and storage product vendors (they however support various other size disks too -but 512b sector disk is in most common use probably because windows/DOS/UNIX FS supported them).
In order to support various disk architecture and FS supporting them use fragmentation which of course let you divide the 4k of page size into various fragments of 1, 2, ... 8 fragments per page.
8-fragments per page is the lowest value which translate into the size of a sector. You can of course not use a sector half of it. For I/O of 1 to full 512 byte of data a full sector gets used in one disk write.
Can you post here the steps you used to test this figures :
1) On UFS, how you saw the fragment size of 1 KB?
2) How did you looked at the 512kb I/O ?
1) fstype
2) dtrace script from DTrace Toolkit (bitesize.d)
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LEARN ABOUT NETBSD
mbrlabel
MBRLABEL(8) BSD System Manager's Manual MBRLABEL(8)
NAME
mbrlabel -- update disk label from MBR label(s)
SYNOPSIS
mbrlabel [-fqrw] [-s sector] device
DESCRIPTION
mbrlabel is used to update a NetBSD disk label from the Master Boot Record (MBR) label(s) found on disks that were previously used on
DOS/Windows systems (or other MBR using systems).
mbrlabel scans the MBR contained in the very first block of the disk (or the block specified through the -s flag), then walks through every
extended partition found and generates additional partition entries for the disk from the MBRs found in those extended partitions.
Each MBR partition which does not have an equivalent partition in the disk label (equivalent in having the same size and offset) is added to
the first free partition slot in the disk label. A free partition slot is defined as one with an fstype of 'unused' and a size of zero
('0'). If there are not enough free slots in the disk label, a warning will be issued.
The raw partition (typically partition c, but d on i386 and some other platforms) is left alone during this process.
By default, the proposed changed disk label will be displayed and no disk label update will occur.
Available options:
-f Force an update, even if there has been no change.
-q Performs operations in a quiet fashion.
-r In conjunction with -w, also update the on-disk label.
-s sector Specifies the logical sector number that has to be read from the disk in order to find the MBR. Useful if the disk has remapping
drivers on it and the MBR is located in a non-standard place. Defaults to 0.
-w Update the in-core label if it has been changed. See also -r.
SEE ALSO
disklabel(8), dkctl(8), fdisk(8), mbr(8)
HISTORY
The mbrlabel command appeared in NetBSD 1.4.
BSD
April 5, 2010 BSD