UNIX for Dummies Questions & Answers

Hello,

I would like to create a Lvolume on an already written disk.
Main goal is to NOT format data on this disk. Unfortunately, while trying to mount my LV , I've got this error :
linux-qc44:/ # mount -a
mount: wrong fs type, bad option, bad superblock on /dev/mapper/system-DB,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so

Anyone have an idea ?

Before doing a mount -a, here's what I did :

linux-qc44:/ # pvcreate /dev/sdb
Physical volume "/dev/sdb" successfully created
linux-qc44:/ # vgcreate system /dev/sdb
Volume group "system" successfully created
linux-qc44:/ # lvcreate -l 100%FREE system -n DB
Logical volume "DB" created
linux-qc44:/ # lvdisplay
--- Logical volume ---
LV Name /dev/system/DB
VG Name system
LV UUID WcEgQK-7xZB-622K-tSu3-x0AQ-Lzhr-fLgHxE
LV Write Access read/write
LV Status available
# open 0
LV Size 1020.00 MB
Current LE 255
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0

When you create a LV you also have to create a FS (Filesystem) of some type on the LV to be able to mount it. Look into the command mkfs maybe.
LVs without FS can just be used for things like RAW volumes etc.

Hi Zaxxon,

thanks for your quick reply.
Unfortunately if Im using mkfs, all preexisting data will be lost.

Let me explain my scenario :
We have two sites.
Site 1 has an AIX connected to a Storage through iscsi protocol. This is the production site. This AIX server use LVM to create VG, PV, LV with no problem.(LV command is formating.

Site 2 (disaster Site) has a second SAN Storage which is receiving mirrored data from Site 1. A second AIX server is attached to this second Storage through iscsi ( this LUN is a data replication from Site 1)
The idea would be to mount the LUN ( which is already populated) on the second AIX through LVM. This is where I get Stuck as I cannot create an LV and mount the system until I do a MKFS !!!!
Is this a normal behavior ? did I miss something ?

Thanks a lot
Ivan

The commands you showed etc. is a Linux box. Now it is 2 AIX boxes? They have totally different commands for their LVMs.

Normal behaviour depends. Usually your AIX1 node has exclusive access rights on the storage and so there is usually a reservation on the SAN-volumes. There are scenarios where there are drivers used, that don't handle reservations. Normal behaviour is often to have only 1 node getting exclusive access to your production box. The other node is often just a standby box. But that all depends on how your scenario is set up.
Without knowing that concurrent access from your second node AIX2 is explicit allowed, I would not touch it.

The normal way is to add your LV and FS from the active productive node AIX1.
Maybe you get some more information how your boxes and SAN-access are setup before daring data corruption or problems for the production node AIX1.

You're right this is some Linux Output .
I currently do not have my AIX available, So I've decided to test on LInux. I thought LVM behaviour was the same on both AIX and LInux.

Is the following make sense to you :

Site 1 :
Storage 1 : Volume and LUN presented to AIX 1 only : readwritable. ( LVM was used to create vg, pv, lv on the presented LUN)

Site 2:
Storage 2 : replicated Volume and LUN presented to AIX 2 only : read-only (until mirror is manually broken (disaster recoery scenario).

Suppose disaster recovery occurs, mirror is manually broken : LUN is getting read write attribute and of course Data are already present on the LUN.
HOW do I proceed to mount this LUN to my AIX WITHOUT FORMATING ??

Any idea ?
Thanks
Ivan

Well what you are trying will surely not work...
If I follow you, the idea is to show via SAN the disk to a remote server ,am I right?
In this case you should not use vgcreate or whatever but make a safe copy using vgexport or exportvg (aix) look at the man pages since I dont have the syntax in mind :
A mistake and you are doomed... I would say in HPUX you would use
vgexport -s -p -m -v mapfile.vgXX /dev/vgXX

using the mapfile you on the remote box can import the vg giving it a newname and hope you mount it read only or use the -e (exclusive) mode

This is what we are to do when using HACMP(AIX) or MCSG (HP)... (but can be done without the soft...)

Hi Vbe,

This is a remote Server on a SECOND SAN . There are 2 replicated SAN. So Volumes ( and LUN) inside SAN 1 is replicated to SAN 2. That's why I don't understand why I have to Format or export something ( as my replication occurs at block level). ??

Thanks a lot.
Ivan