06-12-2014
Blockdev vs /sys/block/
Hello,
I want to set/get the read-ahead for my disks and there is a little issue that confuses me. There are three ways to get/set the read-ahead buffer:
1. cat /sys/block/md0/bdi/read_ahead_kb
2. cat /sys/block/md0/queue/read_ahead_kb
3. blockdev --getra /dev/md0
Which one is the correct one? The first two gives me a value of 128. The last one gives me a value of 256. Where does this difference come from?
10 More Discussions You Might Find Interesting
1. Post Here to Contact Site Administrators and Moderators
What happend to the Administration board, How come no one posts there? (1 Reply)
Discussion started by: tovsky
1 Replies
2. UNIX for Dummies Questions & Answers
Since I failed a test that I didn't have the chance to study for, my wonderful instructor told me to write a paper about BSD sys 5. I can't find anything...does it even exist yet??? If you have any input, I would love you forever if you can enlighten me ASAP. (2 Replies)
Discussion started by: Toughgirl27
2 Replies
3. Shell Programming and Scripting
Hi,
i need a shell script that write in a file called sys.txt this:
<output of date command>
HN <host name>
OS <OS name> <OS version>
I can have this info with uname command, but I can't write these in sys.txt.
Can any one help me? (1 Reply)
Discussion started by: FastMagister
1 Replies
4. Solaris
Hi
I would like to know the difference between System V release and BSD style release.
Regards,
Raja (2 Replies)
Discussion started by: RajaRC
2 Replies
5. Solaris
Hello Guys, im new to this forum. Im from UK and ive recently completed my SCSA I & II and also got trained in Veritas Suite (Veritas Volume Manager and Veritas Clusters, Veritas NetBackup), SAN Configuration. I was trying to get a break as a junior sun solaris admin. I am applying for the jobs... (1 Reply)
Discussion started by: megadeth
1 Replies
6. Programming
How should I use errno in a c program and what info does it have .
I am working with directories and files.
So can any one tell me How to access errno?I am using the stat() function on \etc directory and I am alble to access only the half of the directories.I am not able to access other half and... (6 Replies)
Discussion started by: vijlak
6 Replies
7. What is on Your Mind?
Hi, my name is wesly. I an IT tech at the Junior Level. I have a bachelors degree in Computer Information Systems. I would like to fully become a Unix Sys Admin. Can anyone please tell me what I have to do. Do I have to set up a Unix or Linux server. How about Apache. Please give me clues and tips... (1 Reply)
Discussion started by: wes.lat
1 Replies
8. Solaris
Hi,
I am planning to get certified in Solaris 10 for my own interest.
Although I don't have much experience in sys admin, I have got some background in scripting and some sort of beginner level administration.
But I have read in many places that one must have a good amount of experience in sys... (8 Replies)
Discussion started by: King Nothing
8 Replies
9. UNIX for Dummies Questions & Answers
Dear All,
I am trying to config a sys mail message on solaris 10.
I am doing the following commands but it dose not work with me;
#touch /var/mail-test
#vi /etc/syslog.cong
local0.notice /var/mail-test
#svcadm disable svcs:/system/system-log:default
#svcadm enable... (1 Reply)
Discussion started by: ahmedamer12
1 Replies
10. Programming
(Apologies for any typos.)
OSX 10.12.3 AND Windows 10.
This is for the serious Python experts on at least 3.5.x and above...
In script format sys.stdout.write() AND sys.stderr.write() seems to work correctly.
Have I found a serious bug in the interactive sys.stdout.write() AND... (2 Replies)
Discussion started by: wisecracker
2 Replies
LEARN ABOUT LINUX
blockdev
BLOCKDEV(8) System Manager's Manual BLOCKDEV(8)
NAME
blockdev - call block device ioctls from the command line
SYNOPSIS
blockdev [-q] [-v] command [command...] device [device...]
blockdev --report [device...]
DESCRIPTION
The utility blockdev allows one to call block device ioctls from the command line.
OPTIONS
-V Print version and exit.
-q Be quiet.
-v Be verbose.
--report
Print a report for the specified device. It is possible to give multiple devices. If none is given, all devices which appear in
/proc/partitions are shown. Note that the partition StartSec is in 512-byte sectors.
COMMANDS
It is possible to give multiple devices and multiple commands.
--flushbufs
Flush buffers.
--getalignoff
Get alignment offset.
--getbsz
Print blocksize in bytes.
--getdiscardzeroes
Get discard zeroes support status.
--getfra
Get filesystem readahead in 512-byte sectors.
--getiomin
Get minimum I/O size.
--getioopt
Get optimal I/O size.
--getmaxsect
Get max sectors per request
--getpbsz
Get physical block (sector) size.
--getra
Print readahead (in 512-byte sectors).
--getro
Get read-only. Print 1 if the device is read-only, 0 otherwise.
--getsize64
Print device size in bytes.
--getsize
Print device size (32-bit!) in sectors. Deprecated in favor of the --getsz option.
--getss
Print sectorsize in bytes - usually 512.
--getsz
Get size in 512-byte sectors.
--rereadpt
Reread partition table
--setbsz bytes
Set blocksize.
--setfra sectors
Set filesystem readahead (same like --setra on 2.6 kernels).
--setra sectors
Set readahead (in 512-byte sectors).
--setro
Set read-only.
--setrw
Set read-write.
AUTHOR
blockdev was written by Andries E. Brouwer and rewritten by Karel Zak.
AVAILABILITY
The blockdev command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
Aug 2010 BLOCKDEV(8)