Sponsored Content
Full Discussion: Blockdev vs /sys/block/
Special Forums Hardware Filesystems, Disks and Memory Blockdev vs /sys/block/ Post 302905586 by Sergiu-IT on Thursday 12th of June 2014 08:53:05 AM
Old 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

Sys Administration

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

BSD Sys 5????

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

sys info script

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

Differences Sys 5 and BSD

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

Any sys admins from uk?

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

Hi errno in sys/stat.h

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?

Network Sys Admin

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

Sys Admin Certification

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

need help about config. sys message.

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

Interactive Python 3.5+ sys.stdout.write() AND sys.stderr.write() bug?

(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
LSRAID(8)							Linus md Utilities							 LSRAID(8)

NAME
lsraid - List and query Linux md devices. SYNOPSIS
lsraid -A [-g|-s|-f] {-a <device> | -d <device>} ... lsraid -A -p lsraid -D [-l] {-a <device> | -d <device>} ... lsraid -D -p lsraid -R {-a <device> | -d <device>} ... lsraid -R -p lsraid -h lsraid -V DESCRIPTION
lsraid is a program for querying Linux md devices. It can describe the composite device and the block devices that belong to it. It can also provide a description of the md device suitable for including in the /etc/raidtab configuration file. lsraid also has the ability to operate on online and offline devices. It can read an online device via the kernel interface and provide information about it. When a device is offline, lsraid can look at any of the block devices that are a part of the md device and read the persistent md superblock for information. OPTIONS
-A Selects array-based operation. lsraid will query the given devices and output a short listing of the referenced md devices. -a <device> Adds md device <device> to the list of devices to query. If the device is online, lsraid will discover all of the block devices that belong to it via the kernel interface. Otherwise lsraid will only be able to verify that the device exists. -D Selects disk-based operation. lsraid will query the given devices and then output a description of all the member disks requested. -d <device> Adds block device <device> to the list of devices to query. lsraid will read the md superblock off of <device> and use it to discover the assocated md device and block devices. -f Displays only failed block devices in array-based mode (-A). -g Displays only good block devices in array-based mode (-A). -h, --help Displays a short usage message, then exits. -l Displays a long dump of block device superblocks in disk-based mode (-D). This output is verbatim from the on-disk md superblock, and reflects the state on the specific disk, not the state the md device currently considers authorative. -p Scans all block devices in /proc/partitions for RAID arrays. This can be slow in the presence of network block devices and the like. This option is mutually exclusive with the -a and -d options. -R Selects raidtab operation. lsraid will query all the devices specified and output a description of the referenced md devices in a for- mat suitable for placing in a raidtab(5) file. -s Displays only spare block devices in array-based mode (-A). NOTES
lsraid cannot discover the block devices that make up an offline md device. Providing one of the member devices with the -d option allows lsraid to discover the rest of the information about the offline md device. Disk-based operation only displays the block devices specified on the command line. Specify the md device on the command line to see information about all of the member disks. If the md device is offline, specify both the md device and one of the member disks. lsraid does not do any special handling of md devices composed of other md devices (eg RAID 1+0). The member devices are merely treated as block devices while in the context of the parent device. This is only an issue for raidtab-based operation. The raidtab(5) output will be printed in the order the md devices are queried. This means that a command creating a raidtab(5) for a RAID 1+0 device should list the member devices first on the command line. EXAMPLES
lsraid -A -a /dev/md0 Display a short listing of the md0 device. lsraid -A -d /dev/sda1 Display a short listing of the array that sda1 belongs to. lsraid -A -f -a /dev/md0 Display the failed devices belonging to the md0 device. lsraid -D -l -a /dev/md0 Display a long dump of the on-disk md superblock of every disk in md0. lsraid -D -a /dev/md0 -d /dev/sda1 Display a short discription of the disks in md0 as well as a short description of the disk sda1. sda1 will only be described once if it belongs to md0. lsraid -R -a /dev/md0 -a /dev/md1 -a /dev/md2 Display a description of the arrays in an output format suitable for using in raidtab(5) files. Note that if md0 and md1 are raid0 arrays and md2 is a raid1 created from md0 and md1, this command will output the information in the correct order. lsraid -R -p Scan all block devices in /proc/partitions and display all discovered md devices in a format suitable for using in raidtab(5) files. BUGS
Probably. SEE ALSO
mkraid(8), raidtab(5), raidstart(8), raidstop(8) VERSION
lsraid version 0.7.0 (26 March 2002) HISTORY
Version 0.7.0 Added scanning of active block device partitions. Version 0.4.0 Initial documented version. Functionally complete. AUTHOR
Joel Becker <joel.becker@oracle.com> COPYRIGHT
Copyright (C) Oracle Corporation, Joel Becker. All rights reserved. This program is free software; see the file COPYING in the source distribution for the terms under which it can be redistributed and/or modified. 3rd Berkeley Distribution 2002-03-26 LSRAID(8)
All times are GMT -4. The time now is 09:37 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy