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create logical volume

 
Yaroki
Super Advisor

create logical volume

Hi,

 

I would like to know why I should run the command

# vgcreate /vg01 /dev/dsk/DISK_NAME (block)

 

and not

 

# vgcreate /vg01 /dev/rdsk/DISK_NAME (character)

 

Or maybe I can (?) What would be the differences?

 

BR,

 

Yali

 

2 REPLIES 2
VK2COT
Honored Contributor

Re: create logical volume

Hello,

 

You need to use the block device for physical volumes when using vgcreate(1M) command:

 

 pv_path             The block device path name of a physical
                             volume that will be assigned to the new
                             volume group.

 

If you try to use raw device path, vgcreate(1M) should fail.

 

When accessing a device via a block mode DSF, the system reads and writes data

through a buffer in memory, rather than transferring the data directly to the physical disk.

In other words, normally, the block device is cached. I/O to the device is read into memory,

referred to as buffer cache, in large blocks.

 

To be frank, one of these days, all these commands will become obsolete as far

as type of device we put on the command line. The commands themselves

should choose the right mode. When I teach HP-UX courses, students make

lot of mistakes and cannot remember that, for example:

 

pvcreate requires raw devices

vgcreate requires block devices

diskinfo requires raw device

and so on,

 

Very puzzling for some :)

 

Regards,

VK2COT - Dusan Baljevic
Highlighted
Yaroki
Super Advisor

Re: create logical volume

Hello,

 

Thanks for the reply.

Can you point what is the reason for using raw device path, vgcreate sould fail?

 

BR,

 

Yali