Help in Understanding LVG -> LUN->Controllers.

[Simon M Appleby]

Hi Everybody,

Another question for the Guru's.

Is there documentation, or something of that type, in regards to the relationship of configuring a Filesystem to a LUN then to a LUN then to a Controller (I think it is that way around). I wish too understand the relationships in the configuration. I feel there is a lack of "User Friendly" material in this respect.

Thanks

[Marc Dijkstra]

Check out http://www.docs.hp.com/hpux/os/11.0/index.html and the "HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide (HP-UX 11.0, HP-UX 11i, HP-UX 11i Version 1.5)" doc. Gives a nice overview of the layout.

MND

[Simon M Appleby]

FAO Marc Dijkstra,

Thanks for the pointer, however is the documenetation assuming you are using the "JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide (HP-UX 11.0, HP-UX 11i, HP-UX 11i Version 1.5)". I am having to use a inherit system HP10.20 and they have the SAM and other simular "wizzy" bits switched off and that's (So I have been instructed) the way it is to stay. Ah well!. Any help.

[Marc Dijkstra · Accepted solution]

Righty-ho!

http://www.docs.hp.com/hpux/os/10.x/index.html

Specifically this link.

http://www.docs.hp.com/hpux/onlinedocs/B2355-90672/B2355-90672.html

MND

[Hartmut Lang]

Maybe your problem is, that you mix AutoRAID wordings (LUN), with LVM wordings (LVG).
Both systems work almost independent from each other.

To make use of an AutoRAID , you have to assign physical space of the AutoRAID to LUNs. These LUNs can be used like normal physical disks in LVM.

LUNs/Physical disks can be grouped to LVG.

LVGs can be partioned in lVols.

lVols can be used for Filesystems, swap, ...

[Simon M Appleby]

FAO : Hartmut Lang.

Yep I think the I have a problem in understanding the terminolgy as well as the relationships. The problem is I have min experience with the HP's and more especially the AutoRaids. The boss point a figure in my direction because I am a Ingres DBA therefore the transision to HP DBA is easy, yer right!. Can you help me to understand from scratch. Meaning I have a disk 18Gb say and wish to attch to a controller then I think a Vg which in turn has Lvg's and then assign them to a Lun or two. Maybe's thats right or wrong I am not sure that is why I need some sort of whitepapaer or explaination of howto.

Hope you can help

[Roger Baptiste]

Simon,

There are different layers in the disk/vg setup.

At the lowest is the Hardware - the disks themselves. In the simplest
case, you would have One *physical disk* being used as *one physical disk*. eg: the internal root disks of the system or the disk on your PC! But, in RAID Disks, we have a group of disks which are grouped together , configured according to a level (raid 1, 5, 0/1 .. don''t worry ) and are presented to the system
as a LUN. (logical unit).
The point is what you see on the system as a disk is actually a group of disk slices in the Raid array . Again not to worry on the gory details,if you understood the concept.
The reason we have the RAIDs is for data protection, flexible usage, speed etc.

Configuration of RAIDS is done at the disk and has nothing to do with the VG or higher layers. Each disk vendor have their own methods and software to configure the RAIDS.

Once the Raid is configured, you should be able to see the LUN's being presented to the system for use. (ioscan -nfCdisk will list the disks(luns) and a diskinfo on these lun paths will give more info).

From here on, you can treat these luns are regular disks for VG configuration. You move on to the next higher layer.

You would select disks and group them into a Volumegroup by running the VGcreate command. VG is nothing but a logical grouping of LUNS as one whole disk Unit available for use.

From the VG, you can create logicalvolumes and then
create filesystems over them for putting it to actual use.

This is a simple, overall view. The best way to know it better is to actually creating it!

HTH
raj

[Sridhar Bhaskarla]

Hi Simon,

LUN is the Logical Unit device that is seen as a "single disk" on the system.

The configuration of LUN is done on the disk array subsystem you have. It could be a combination of disks or a single disk itself. Or it could be a slice of a set of RAID5 disks. It can be alloted with a uniq logical number called LUN id.This entire setup is dependent on the configuration of the disk subsystem.

Once the array is connected to the system, it is seen as a disk with it's LUN id appearing associated with d in cxtydz device file. This is basically the nominclature of the device files

cx - Controller at the instance "x". This is the hardware interface on the system. The system will allot a pointer to this device called "instance number" that can be found in the ioscan output.
ty - Target number
dz - disk or LUN number

dz is limited to 15. If your LUN number is more than 15, they will appear as t1d0 onwards.

This disk is now configured into Volume groups. Physical Volume Groups are groups of disks configured in a volume group. This is completely optional.

You can go through the following manuals to get an idea of this terminology.

http://www.hp.com/cposupport/manindex/hpsurestor19162_eng_man.html

-Sri

[Simon M Appleby]

FAO : Raj.

Thanks for the info and now I understand more or less the concept (without the gory bits). I have tried the "ioscan" but I seem unable to use it, in fact in seems to to reside on the system !!!!. Anyway, I have tried a cmd "lvdisplay -v" which seems to give some very useful info. However is there any simiular cmd that will show the relationship of the Luns in respect to the "lvdisplay" cmd ?. Is there any way I can do something simular as ioscan to as you say "list the luns and pathways" ?.

FAO : Sri.

Thank you, useful pointer to useful information.

[Roger Baptiste]

<>

Don''t worry , you will get to know the gory stuff after setting it up and working on it for some time.

>

It should be in the system.
Try /usr/sbin/ioscan
(or /etc/ioscan).
Probably your PATH variable doesn''t include /usr/sbin in it.
Typical output of ioscan would be like this:
#ioscan -nfCdisk
Class I H/W Path Driver S/W State H/W Type Description
==================================================================================
disk 2 0/0/1/0.1.0 sdisk CLAIMED DEVICE HP DVD-ROM 6x/32x
/dev/dsk/c0t1d0 /dev/rdsk/c0t1d0
disk 0 0/0/2/0.6.0 sdisk CLAIMED DEVICE SEAGATE ST39103LC
/dev/dsk/c1t6d0 /dev/rdsk/c1t6d0
disk 1 0/0/2/1.6.0 sdisk CLAIMED DEVICE SEAGATE ST39103LC
/dev/dsk/c2t6d0 /dev/rdsk/c2t6d0
disk 3 0/4/0/0.8.0.18.0.0.0 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c5t0d0 /dev/rdsk/c5t0d0
disk 423 0/4/0/0.8.0.18.0.6.0 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c5t6d0 /dev/rdsk/c5t6d0
disk 424 0/4/0/0.8.0.18.0.6.1 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c5t6d1 /dev/rdsk/c5t6d1
disk 425 0/4/0/0.8.0.18.0.6.2 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c5t6d2 /dev/rdsk/c5t6d2
disk 426 0/4/0/0.8.0.18.0.6.3 sdisk CLAIMED DEVICE EMC SYMMETRIX
/dev/dsk/c5t6d3 /dev/rdsk/c5t6d3
*****

As you see in the sample, it lists EMC lun's (since that''s what i have ).


<>

lvdisplay gives useful info on the LV configuration, but that will come much later in the pyramid of disk to LV layers.

>

ioscan is a key command (not just for disks but pretty much all the H/w on the box).

Useful commands:

ioscan -nfCdisk -> shows disks(or luns) seen by the system

diskinfo /dev/rdsk/cxtydz
-> gives info on each disk/lun shown by the ioscan

pvdisplay /dev/dsk/cxtydz
-> shows info on whether the disk/lun is a part of Volumegroup or not.

vgdisplay -v -> shows info on the Volumegroups present in the ssytem. It displays what disks each volumegroup contains and also the logical volumes present in each Volumegroup

lvdisplay -v /dev/vgxx/lvxx -> gives details about each logical volume

Commands to create pv''s, vg''s, lv would be
pvcreate, vgcreate and lvcreate
with tonnes of options to go along with them.

You can also use SAM to help
you view the above details, but that would only postpone learning the commands for a later time!

At the RAID level, commands to view the Lun's would differ depending on the manufacturer. For eg, in EMC the commands are inq, syminq ..

HTH
raj