02-09-2013
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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LEARN ABOUT OSF1
extendfs
extendfs(8) System Manager's Manual extendfs(8)
NAME
extendfs - Extends UFS file systems
SYNOPSIS
/sbin/extendfs [- s] [disk_blocks] device_name
DESCRIPTION
Use the extendfs command to increase the storage space in a UFS file system. The file system must not be mounted when you perform this
operation. To extend a mounted (in use) UFS file system, use the mount command with the -o extend option.
The procedure for increasing the storage space of a UFS file system is as follows: Look at the contents the /etc/fstab file to identify the
disk partition that maps to the file system. Ensure that there is available storage space on the target disk as follows: If LSM is in use
on your system, use LSM commands to increase the size of the LSM volume as described in the Logical Storage Manager guide. If LSM is not
in use on your system, use the disklabel command or the diskconfig graphical user interface to check the current size and use of partitions
on the disk. If there is adequate space on an adjacent partition, use the disklabel command to write the current label to a file as fol-
lows: # disklabel -r dsk4 > d4label Edit the disklabel file to change the size of the partition on which your UFS file system resides.
Increase the number of disk blocks on the partition and decrease the disk block size of the adjacent partition by an equivalent number.
Use the disklabel command with the -R option to write the revised label to the raw disk as follows: # disklabel -R /dev/rdisk/dsk4 d4label
When the disk label is revised, extend the file system using the extendfs command. You can either use the full extent of the newly sized
partition or extend the file system in stages. The following example commands show both methods. To extend the file system to use all the
available space, you specify the disk partition on which the file system resides, as follows: # extendfs /dev/disk/dsk4g To extend the
file system to use only part of the available space, you specify a number of disk blocks, as follows: # extendfs -s 300000 /dev/disk/dsk4g
The remainder of the extended partion is reserved for future use.
You can extend a file system as many times as necessary, up to the physical limit of the storage device. When no more space is available
on the storage device, you must back up the file system using the dump command and restore the file system to a storage device that has
more available space.
Once you have extended a file system, the operation cannot be reversed except by a back up and restore operation. Use the dump command to
back up the file system. You can then reset the partition sizes manually and restore the file system to the storage device.
ERRORS
The disklabel command produces output similar to that of the newfs command. If a list of disk blocks is not displayed on the terminal, the
command has failed. Verify the partition settings and the mount status of the target file system.
The disklabel command does not permit you to overwrite a partition if it is in use. Refer to the disklabel(8) reference page for more
information on label errors.
FILES
Specifies the command path.
RELATED INFORMATION
diskconfig(8), disklabel(8), mount(8), and fstab(4).
extendfs(8)