topic Re: Quick question in Operating System - HP-UX

Quick question

David Smith_28 — Thu, 29 Jan 2004 08:22:52 GMT

Why do all root logical volumes have the contiguous option set to yes. Is this mandatory. What is the reasoning behind this?
Thanks in advance.

Re: Quick question

Pete Randall — Thu, 29 Jan 2004 08:31:36 GMT

David,

It's mandatory for /stand and swap. The others do not have to be contiguous.

Pete

Re: Quick question

Pete Randall — Thu, 29 Jan 2004 08:32:07 GMT

David,

Oh - and the reason is so the boot loader knows where to find things.

Pete

Re: Quick question

Marco Santerre — Thu, 29 Jan 2004 08:33:28 GMT

It is not a mandatory thing except for one or two.. If I remember correctly .. you need to have /stand contiguous and maybe your swap space.

Re: Quick question

John Carr_2 — Thu, 29 Jan 2004 08:34:40 GMT

HP recommend root stand and swap to be contigous . The boot loader needs to know where to start reading the kernel from on the disk and be able to continue to read it sequentially.

John.

Re: Quick question

Sridhar Bhaskarla — Thu, 29 Jan 2004 08:34:41 GMT

Hi,

root is also to be contiguous. In fact all the logical volumes that appear in lvlnboot are to be contiguous.

-Sri

Re: Quick question

Leif Halvarsson_2 — Thu, 29 Jan 2004 08:38:05 GMT

Hi,
Check the man page for lvlnboot. The following volumes need to be contiguos:

/
/stand
swap
dump

Re: Quick question

Pete Randall — Thu, 29 Jan 2004 08:38:32 GMT

Sorry, David - I missed on / - it should be contiguous as well. In a normal installation, the other lvols end up being "strict" but not "contiguous", by the way.

Pete

Re: Quick question

Chris Wilshaw — Thu, 29 Jan 2004 08:39:42 GMT

As others have stated, some of the volumes have to be contiguous.

The others are all contiguous as a default, because the installation process takes the next free set of extents when the volume is created.

If you were to later extend one of the filesystems (/home for example), the Allocation marker changes

On one of our systems, we created a 100MB home filesystem, and later extended this to 200MG. As you can see, Allocation is now listed as "strict", not "strict/contiguous"

--- Logical volumes ---
LV Name /dev/vg00/lvol4
VG Name /dev/vg00
LV Permission read/write
LV Status available/syncd
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 200
Current LE 50
Allocated PE 100
Stripes 0
Stripe Size (Kbytes) 0
Bad block on
Allocation strict
IO Timeout (Seconds) default

Re: Quick question

Sridhar Bhaskarla — Thu, 29 Jan 2004 08:59:31 GMT

I missed the reason.

My understanding is that the kernel loads the LVM related drivers. So, prior to loading of the kernel there is no way for the boot process to find the non-contiguous blocks as it wouldn't understand the LVM structure.

-Sri