Will anybody pls explain it

[sinhass]

I want to share my experience but don't have explanation. Anyone pls explain me.

I have seen that data from a disk can be recovered without any vgcfgbackup/vgimport file if it is
1.single disk volume group.
2.single lvm and file system in that vg.

I just created vg & lv with sam and unticked the create new fs button. then just mounted file system and it worked ! I did it so many times with 10.20 but don't know how it works. There was no mirrordisk/ux

[Pete Randall · Accepted solution]

Creating the vg & lv only rewrite the LVM structures on the disk without affecting any other data. If the disk previously had a file system on it, it is entirely plausible that it would be accessible as long as newfs was not run.


Pete

[Helen French]

If you don't create file system on the LV, you can use it as a 'raw' device (for eg: in Oracle). In this case, you are not using any file system advantages, but get faster performance.

Also, you don't need Mirror/UX for creating file systems or using it. Mirror/UX is for mirroring (two disks has the same data) between two LVs.

[Jeff Schussele]

Congratulations Sinhass - you're the proud father of a brand spanking new Raw Volume!

Best Rgds,
Jeff

[A. Clay Stephenson]

Because the LVM structures are at the front ent of the disk. If you create a vg using an existing disk and accept the default parameters, lvol1 will start in exactly the same place on the disk. The old filesyste data structures will still be in place. There is a danger because this is simply working by accident. Suppose that originally lvol1 was 4000MB and the new one is 2000MB. The filesystem has not been resized so there will be inaccessable data that might not show up for quite a while or at the very least the filesystem will now contain blocks that are not accessible. You should always use vgimport to do this and you will never have problems.

[sinhass]

Thanks all of U. I got my answer.
-sinhass