What is the difference between o_direct and DAX with ext4 filesystem? Post: 302982214

10 More Discussions You Might Find Interesting

1. Filesystems, Disks and Memory

Gfs2 vs xfs vs ext4

Looking for suggestions as to which filesystem to go with. I currently use gfs2 on hosts with 3.4tb useable. I understand gfs2 is being left behind but xfs and ext4 are not quite certified completely on CentOS 5.2. I have email storage hosts that have a decent i/o requirement and 12TB usable after...

2. Filesystems, Disks and Memory

ext4 - ready for production system?

Gidday, Are you using ext4 for production system? Or is it better to opt for a more conservative strategy, like ext3 for instance? What are your experiences? Thanks in advance, Lo�c.

3. Solaris

Difference between filesystem and partition

wht is major difference between filesystem & partition

4. Programming

Writing files using O_DIRECT in C

I am trying to write .pgm images using the O_DIRECT flag in open(). I have a char* buffer which has the image data. I know that I have to align the buffers and have done that using posix_memalign() yet only a part of the image gets written. Has someone used O_DIRECT for writing files...

5. Shell Programming and Scripting

Testing for O_DIRECT support

Is there some was to test if opening with the O_DIRECT flag will work (without writing a C program)?

6. Programming

Kernel programming - Ext4 and extents contents

Hi there, I have a problem with Unix kernel programming. I have to write a program who should output the whole information the EXT4 extents contain. I have found many tutorial and information about how the EXT4 filesystem is working. Also There ar many information about the EXT4 structure but I...

7. Red Hat

Convert ext4 to ext3

Is there any way to conver ext4 to ext3 filesystem without formatting the partition/disk .. Had ext3 filesystem and had converted it to ext4 by issuing following command # tune2fs -O extents,uninit_bg,dir_index /dev/sda1 # fsck -pf /dev/sda1 # blkid /dev/sda1 /dev/sda1:...

8. Solaris

Unable to mount ext4 filesystem (created from Ubuntu) in Solaris 11

Hello everyone, I am trying to mount an ext4 filesystem which I created from Ubuntu. But mount command fails saying: prakhar@Solaris:~$ sudo mount /dev/dsk/c10t0d0p1 /mnt Password: mount: /dev/dsk/c10t0d0p1 is not this fstype And I also tried this: prakhar@Solaris:~$ fstyp...

9. Red Hat

Shrink ext4 filesystem and reduce the size of a Logical Volume in Linux

Hello guys, I would like to ask you kindly if you don't know some quick and safe method how to shrink ext4 filesystem and reduce the size of a Logical Volume in Linux, please? Thank you very much.

10. Solaris

DAX fallbacks

Hi, could you explain what DAX fallbacks mean in detail and how to avoid them? Or is it ok to have fallbacks? Unfortunately googling does not help... MANpage says: fallbacks == Number of commands completed by the software, which DAX could not complete OK, but why and what does...

LEARN ABOUT REDHAT

pnmpsnr

pnmpsnr(1)						      General Commands Manual							pnmpsnr(1)

NAME

       pnmpsnr - compute the difference between two images (the PSNR)

SYNOPSIS

       pnmpsnr [pnmfile1] [pnmfile2]

DESCRIPTION

       Reads  two  PBM,  PGM, or PPM files, or PAM equivalents, as input.  Prints the peak signal-to-noise ratio (PSNR) difference between the two
       images.	This metric is typically used in image compression papers to rate the distortion between original and decoded image.

       If the inputs are PBM or PGM, pnmpsnr prints the PSNR of the luminance only.  Otherwise, it prints the separate PSNRs of the luminance, and
       chrominance (Cb and Cr) components of the colors.

       The  PSNR  of  a  given component is the ratio of the mean square difference of the component for the two images to the maximum mean square
       difference that can exist betwee any two images.  It is expressed as a decibel value.

       The mean square difference of a component for two images is the mean square difference of the component value, comparing  each  pixel  with
       the pixel in the same position of the other image.  For the purposes of this computation, components are normalized to the scale [0..1].

       The maximum mean square difference is identically 1.

       So the higher the PSNR, the closer the images are.  A luminance PSNR of 20 means the mean square difference of the luminances of the pixels
       is 100 times less than the maximum possible difference, i.e. 0.01.

SEE ALSO

       pnm(5)

								   04 March 2001							pnmpsnr(1)

10 More Discussions You Might Find Interesting

1. Filesystems, Disks and Memory

Gfs2 vs xfs vs ext4

Discussion started by: king_hippo

2. Filesystems, Disks and Memory

ext4 - ready for production system?

Discussion started by: Loic Domaigne

3. Solaris

Difference between filesystem and partition

Discussion started by: rajaramrnb

4. Programming

Writing files using O_DIRECT in C

Discussion started by: anchit87