How to check LDEV in server?

Linux and Unix-Like Red Hat
1

Hi ,

There is one task to provide 50 GB space to the disk group ORABACK and Storage team have confirmed saying allocated below LDEV with 50 GB
03:90.
How to check LDEV with 50 GB is created in server ?Could you please guide me ?

$ cat /etc/redhat-release
Red Hat Enterprise Linux Server release 6.6 (Santiago)

$ uname -a
Linux saecopd510.europe.nokia.com 2.6.32-504.8.1.el6.x86_64 #1 SMP Fri Dec 19 12:09:25 EST 2014 x86_64 x86_64 x86_64 GNU/Linux

Regards,
Maddy

2

Did the storage administrators provide you with a LUN corresponding to the LDEV? What make of storage device?

3

Hi Murphy,

Yes, it is 03:90.

Here is the mail confirmation from storage admin.

Hi,

As per subject change we have allocated below LDEV with 50GB, please check and confirm the same.

03:90.

Regards,
Maddy

4

If you are using dm multipath...

Rescan the fabric (all ports) using echo or 3rd party utilities.
multipath -ll should now show the new lun, else restart the deamon.

You will see the mpath<number> (largenumberLUNID) and other info about the new lun.

Also, check ls -lrt /dev/mapper/* , for the newest device created named mpath<number> corresponding with output of multipath.

If you are using multipath.conf for naming your devices (which i recommend), now is the time to change the name to your liking and restart the deamon.
If you used your custom name in multipath.conf, it will be created under /dev/mapper/yourname.

You can can use the new device in the operating system, using the /dev/mapper/devicename. Be sure to use /dev/mapper not /dev/mpath or other.

Hope that helps
Regards
Peasant.

5

Hi Peasant,

That was very well explained.Thanks for that.
I am able to see the new device created as below.

$ ls -alrt /dev/mapper/HDS_K1_0390_41
lrwxrwxrwx. 1 root root 8 Feb 27 16:40 /dev/mapper/HDS_K1_0390_41 -> ../dm-45

$ ls -lrt /dev/mapper/*
crw-rw----. 1 root root 10, 58 Feb 12 08:36 /dev/mapper/control
lrwxrwxrwx. 1 root root      8 Feb 27 16:40 /dev/mapper/HDS_K1_0390_41p1 -> ../dm-46
lrwxrwxrwx. 1 root root      8 Feb 27 16:40 /dev/mapper/HDS_K1_0390_41 -> ../dm-45

How to determine the new device was created with 50 GB size in OS level ?I am able to see the size of new device in the database instance.

SQL> select path,os_mb ,header_status from v$asm_disk where header_status in ('CANDIDATE','FORMER') order by 2;

PATH                                OS_MB HEADER_STATUS
------------------------------ ---------- ------------------------------------
/dev/raw/raw41                      51199 CANDIDATE
/dev/raw/raw36                     102398 CANDIDATE
/dev/raw/raw35                     102398 CANDIDATE

Yes, we are using multipath.conf i guess and i am scared to change the name of the device since i don't know what is daemon and the command to restart and the impact if i restart and hence can't do it :slight_smile:

I don't have any name created in OS.

I dont't know how to rescan the fabric and the impact of it.Hence can't do it :slight_smile:

Regards,
Maddy

6

That's is ASM right ?
If the ASM sees the new disk, it is fine. ASM is like a volumegroup/filesystem for oracle databases, if you can add it and see it after, the disk is fine.

From this perspective, looks like someone already did the initial setup for new disk, since you see it, and it has a defined name (HDS... not default one) present probably from Hitachi storage by name :wink:

What bothers me is using /dev/raw devices, it is depriciated, since Oracle ASM will use O_DIRECT flag whatever device you give to him for years now.

It will (and does) work with this setup.

You might just want to check raw -qa to check if bindings are to /dev/mapper devices (they should be).

If not, you might want to fix that, since if you lose one path, there is a chance that database will not be able to access the disk resulting in pain and misery probably :rolleyes:

Hope that clears things out
Regards
Peasant.

7

Hi Peasant,

Thanks for your clarification and it is clear now .

Regards,
Maddy