Difference between /dev/hdisk and /dev/rhdisk Post: 302825089

Sponsored Content

Operating Systems AIX Difference between /dev/hdisk and /dev/rhdisk Post 302825089 by bakunin on Sunday 23rd of June 2013 11:35:46 AM

06-23-2013

Registered User

It usually helps if you ask what you really want to know, instead of something vaguely related to that. We are not adverse to explaining things, but commonly get angry when we get the feeling that we are abused to cover a lack of energy.

Quote:

Originally Posted by jibujacob

I had gone through google prior to posting and couldnot identify whether my filesytem is made of the rawdisks or non-raw disks....

Your filesystem is made of volumes, neither raw nor other disks. That is the point of having a logical volume manager.

There is a driver for each certain (type of) disk: SCSI drives, LUNs, whatever. This driver creates a blockdevice and a character device. If you want to use the device directly, you can do that and, for instance, use a program like "dd" to write to it.

Otherwise you give this device to the LVM, which uses it to create Physical Volumes, PVs. "creating PVs" means it writes all sort of management-information onto it, like the VGDA (volume group descriptor area), etc.. Think of this like taking open (raw) land and build roads, create lots, and so on: the land is still unused, but now the means to use it are there.

Now you create Logical Volumes, LVs, on this now usable space. You can use such an LV like a raw device too (and this is sometimes done, for instance with databases), but it is not the same as the raw devices from before, because now this raw space is under control of the LVM and can be handled by its methods: it can be moved to another PV, increased in size, ...

Finally, you can create a filesystem on such an LV, instead of using the provided space directly. You could also create a swap space, a dump device or something entirely different instead. Depending on what you create a certain driver (for filesystems the filesystem driver) will use the LV to create the entity it is designed to provide.

I hope this clears it up a bit.

bakunin

Last edited by bakunin; 06-23-2013 at 12:43 PM..

bakunin

View Public Profile for bakunin

Find all posts by bakunin

9 More Discussions You Might Find Interesting

1. Solaris

What is /dev/tty /dev/null and /dev/console

Hi, Anyone can help My solaris 8 system has the following /dev/null , /dev/tty and /dev/console All permission are lrwxrwxrwx Can this be change to a non-world write ?? any impact ??

2. UNIX for Dummies Questions & Answers

Sending alt-n to /dev/pts/1 from process bound to /dev/pts/2

Hello, i am using finch (unix commandline instant messaging client using libgnt) which is running connected to /dev/pts/1 Now I would like to "remote control" the program by sending the key combinations normally typed on the keyboard from a programm in another shell. So I tried:...

3. UNIX for Dummies Questions & Answers

Difference between /dev and devices

Please explain me the difference between /dev and devices.. Googled info is - /dev - where logical device names stores here devices - physical device info stores here... Could any one explain me.. the real difference and major one

4. Solaris

Lun remove, stuck in /dev/dsk and /dev/rdsk

So, we removed a LUN from the SAN and the system is refusing to remove the references to it in the /dev folder. I've done the following: devfsadm -Cv powermt -q luxadm -e offline <drive path> luxadm probe All those commands failed to remove the path. The drive stills shows up as <drive...

5. AIX

Problem in /dev/hd1 and /dev/hd9var

Hello AIXians, I can't boot my AIX, it hangs and stops at the code error: 0518 After searching google, I knew the problem is due to problems in File Systems. So the solution is booting from any bootable media, then run these commands in maintenance mode: #fsck -y /dev/hd4 #fsck -y...

6. Shell Programming and Scripting

Automating partitioning setup of /dev/sda on /dev/sdc

Objective: To recreate the partitioning setup of /dev/sda on /dev/sdc How would I parse the below information and initialize variables (an array?) that can be used to build sgdisk commands in a script, regardless of the number of partitions? Something along the lines of: sgdisk -n...

7. AIX

How can I map hdisk# to rhdisk#?

Some storage/disks have been added to an existing AIX 6.1 server. The admin sent me the list of hdisk#'s for the new disks, but I need the corresponding rhdisk# for the same hdisk. (I know from past experience that the rhdisk that maps to an hdisk is not always the same number. For instance,...

8. Red Hat

Changing grub from /dev/sda to /dev/sdb

Hi, Please suggest steps to change grub from /dev/sda to /dev/sdb,

9. HP-UX

Dev/urandom and dev/random missing in HP-UX

Hi, In our HP-UX B.11.11. I could not find dev/urandom and dev/random Are all pseudo-devices implemented as device drivers, or in need to run /configure some package to install the package to have dev/urandom. Please help

LEARN ABOUT CENTOS

fdformat

FDFORMAT(8)						       System Administration						       FDFORMAT(8)

NAME

       fdformat - low-level format a floppy disk

SYNOPSIS

       fdformat [options] device

DESCRIPTION

       fdformat does a low-level format on a floppy disk.  device is usually one of the following (for floppy devices the major = 2, and the minor
       is shown for informational purposes only):

	      /dev/fd0d360  (minor = 4)
	      /dev/fd0h1200 (minor = 8)
	      /dev/fd0D360  (minor = 12)
	      /dev/fd0H360  (minor = 12)
	      /dev/fd0D720  (minor = 16)
	      /dev/fd0H720  (minor = 16)
	      /dev/fd0h360  (minor = 20)
	      /dev/fd0h720  (minor = 24)
	      /dev/fd0H1440 (minor = 28)

	      /dev/fd1d360  (minor = 5)
	      /dev/fd1h1200 (minor = 9)
	      /dev/fd1D360  (minor = 13)
	      /dev/fd1H360  (minor = 13)
	      /dev/fd1D720  (minor = 17)
	      /dev/fd1H720  (minor = 17)
	      /dev/fd1h360  (minor = 21)
	      /dev/fd1h720  (minor = 25)
	      /dev/fd1H1440 (minor = 29)

       The generic floppy devices, /dev/fd0 and /dev/fd1, will fail to work with fdformat when a non-standard format is being used, or if the for-
       mat has not been autodetected earlier.  In this case, use setfdprm(8) to load the disk parameters.

OPTIONS

       -n, --no-verify
	      Skip the verification that is normally performed after the formatting.

       -V, --version
	      Output version information and exit.

       -h, --help
	      Display help and exit.

SEE ALSO

       fd(4), setfdprm(8), mkfs(8), emkfs(8)

AUTHOR

       Werner Almesberger (almesber@nessie.cs.id.ethz.ch)

AVAILABILITY

       The fdformat command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux							     July 2011							       FDFORMAT(8)