LVM pvcreate

[Nath_3]

Hi,

Does pvcreate -f deletes the data on the disk? I am using oracle raw logical volumes.

Thanks

[R.K. #]

Hi Nath,

"pvcreate -f" will NOT delete the data. It will only remove the headers on the disk.
If you have VG backup files (created from vgcfgbackup, normally inside /etc/lvmconf/ directory), then you can revert back (by "vgcfgrestore") and get the disk working as before.

-RK

[Jeeshan]

yeah, absolutely.

whenever you apply command pvcreate, it deletes all the previous data reside in it and clean the disk as like as new disk.

[sujit kumar singh]

hi


the pvcreate is a destructive command that writes the necessary LVM Structures on a disk and after that we add the disk to a VG using vgcreate or vgextend.

used with -f option this deletes the earlier LVM structures on the disk and creates the new one.

LVM structures on a disk are the metadata structures that are used to keep all the informations regarding the LV, VG ,PV, data area , boot area etc.

So all the LVM related information is gone.
that means that u can further do not read any data on the disk.the disk becomes as good as an empty or new disk.


Regards
Sujit

[avizen9]

HI Nath,
i had done this before,
it will remove all your information from that physicall HDD (LVM , VG)

you can not recover all info again. tq

[Duncan Edmonstone · Accepted solution]

you gotta love it when you get completely different answers to these sorts of questions. Guys if your not *completely* sure, say so!

For the record RK has it right. pvcreate overwrites the reserved area at the start of a disk that contains LVM metadata. The actual remaining data on disk is left untouched, and you *should* be able to get it back if you have a backup of the LVM headers in /etc/lvmconf. vgcfgrestore can be used to do that.

Now if you've accidently run a pvcreate -fB on a data disk that wasn't previously bootable, you could really lose data, as the -B option makes the reserved area bigger to provide space for the boot LIF areas. If the disk wasn't previously used for boot, then the first few LVM extents could get overwritten.

HTH

Duncan

[R.K. #]

Hey Duncan,
Nice piece of info about "pvcreate -Bf".
A good point to take care of.
:)

[surendranath]

Is this the same even when data resides on block logical volume?

[Nath_3]

Thanks for the info. I agree with RK and Duncan. And i did a pvcreate -f on a disk and i could get back the all the data.

One more Question regarding the same:

Is this the same even when data resides on block logical volume?

Thanks
Ravi

[Torsten.]

Everything said applies to each LVM physical volume - no matter what is inside the logical volumes.

[likid0]

As previous comments, with pvcreate you ONLY loose your lvm structure, you can restore it with vgcfgrestore.

For example in a one pv vg, you could pvcreate the vg, create a new vg with that pv with the same VG options pe, max_pvs, etc, and then create lvols with exactly the same size as the ones you had before, and you will be able to mount and access the data with no problems.