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..
10 More Discussions You Might Find Interesting
1. UNIX for Dummies Questions & Answers
Hi Everyone,
Can someone tell me the effect of the pp size of the volume group created for Oracle data.
It would seem that creating small pp's will cause more overhead. What if you make the pp to large? What should I base this size on?
Thanks, (4 Replies)
Discussion started by: kburrows
4 Replies
2. AIX
How can I find the filesystem block size in AIX?
I need to check if it is the same as my DB block size. (4 Replies)
Discussion started by: progressdll
4 Replies
3. HP-UX
Hi
is there a cmd in hpux 11 to determine the physical size of the hard disk.
not bdf command.
i have searched the other threads here but cant find an answer.
thank you guys (4 Replies)
Discussion started by: hoffies
4 Replies
4. IP Networking
Hi,
Does anybody know how to get the RAM size of a powerless server (OS off), with a network hardware management protocol like IPMI ???
Thx (0 Replies)
Discussion started by: sncr24
0 Replies
5. UNIX Desktop Questions & Answers
How can I determine the block group size of my filesystem, in case I would like to determine where my backup superblocks are? Or how can I determine the location of my backup superblock?
If usually, for the block group size of 1k, the alternate superblock will be at block 8193.
Thanks, (2 Replies)
Discussion started by: Pouchie1
2 Replies
6. Shell Programming and Scripting
I am pretty new to scripting, so I appreciate your advice in advance.
The problem:
100 directories each containing 2 files that have the same extension with random names. The only attribute that discriminates the files is size. I would like to write a script that compares the files for size... (6 Replies)
Discussion started by: JC_1
6 Replies
7. Solaris
Hi,
kstat -p -m zfs -n arcstats -s size returns
zfs:0:arcstats:size 8177310584
this values is approx (7.61 GB)
but my Physical Memory size is only 6144 Megabytes.
Can this happen ?
if yes, then how can I find free memory on the system.
BTW, I ran the kstat commands from a Non... (2 Replies)
Discussion started by: sapre_amit
2 Replies
8. Shell Programming and Scripting
I have a tar file with name DTT012_GP_20140207.tar and many more with different names of different sizes ranging from 1GB to 4GB.
Now my requirement is to extract/not extract these files and then divide it into various parts of size 500MB and save it with different names and then compress... (5 Replies)
Discussion started by: Shaibal_bp
5 Replies
9. HP-UX
Accordingly a lot of manuals - if you have block size 8KB and trying to write a 1KB file to the block, as result you waste 7KB of the block space. But recently I noticed about Fragments of File Block. In same case if you have File Block 8KB and Fragment size 1KB - you can save your block space,... (6 Replies)
Discussion started by: jess_t03
6 Replies
10. Solaris
Close (0 Replies)
Discussion started by: gull05
0 Replies
LEARN ABOUT NETBSD
scan_lfs
SCAN_FFS(8) BSD System Manager's Manual SCAN_FFS(8)
NAME
scan_ffs, scan_lfs -- find FFSv1/FFSv2/LFS partitions on a disk or file
SYNOPSIS
scan_ffs [-blv] [-e end] [-F file] [-s start] device
DESCRIPTION
scan_ffs will take a raw disk device that covers the whole disk or a file and will find all possible FFSv[12]/LFS partitions, independent of
block sizes on it. It will show the file system type (FFSv1, FFSv2, or LFS), size, and offset. Also it has an option to show the values
with a disklabel-alike output.
The options are as follows:
-b Report every superblock found with its sector address, rather than trying to report the partition boundaries. This option can
be useful to find the other superblocks in a partition if the first superblock has become corrupted. It is most useful if
device refers to the raw device for the partition, rather than the entire disk.
-e end Where to stop searching for file systems. The end argument specifies the last sector that will be searched. Default is the
last sector of device.
-F file Path to a file containing possible partitions inside of it.
-l Print out a string looking much like the input to disklabel. With a little massaging, this output can usually be used by
disklabel(8).
-s start Where to start searching for file systems. This makes it easier to skip swap partitions or other large non-UFS/FFS partitions.
The start argument specifies the first sector that will be searched. Default is the first sector of device.
-v Be verbose about what scan_ffs is doing, and what has been found.
The device argument specifies which device scan_ffs should scan for file systems.
scan_lfs is just another name for the same program, both behave in exactly the same way.
SEE ALSO
disklabel(8)
HISTORY
The scan_ffs program first appeared in OpenBSD 2.3 and then in NetBSD 3.1. Support for searching in files was added in NetBSD 4.0.
AUTHORS
scan_ffs was written for OpenBSD by Niklas Hallqvist and Tobias Weingartner. It was ported to NetBSD by Juan Romero Pardines, who added sup-
port for LFS/FFSv2, partitions with fragsize/blocksize greater than 2048/16384 for FFSv1, searching on files, etc.
BUGS
Currently scan_ffs won't find partitions with fragsize/blocksize greater than 8192/65536.
BSD
May 1, 2007 BSD