[linux-lvm] lvm metadata

[linux-lvm] lvm metadata

[Benoit]

Hello,

I'm wondering why lvm metadata isn't stored directly into physical volumes. It 
would then be possible to read it without having acces to any filesystem. 
You may ask why. Then is my second question, why aren't vgscan and vgchange 
implemented in kernel and called at boot time ? This would make us be able to 
consider logical volumes as standard partitions and mount them easily, even 
as /

Thank you,
Benoit.

PS: Please cc-me with the anser as I'm not subscribed to the list.

Re: [linux-lvm] lvm metadata

[Heinz J . Mauelshagen]

On Tue, Nov 11, 2003 at 11:44:36AM +0100, Benoit wrote:
> Hello,
> 
> I'm wondering why lvm metadata isn't stored directly into physical volumes. It 
> would then be possible to read it without having acces to any filesystem. 

It is.

> You may ask why. Then is my second question, why aren't vgscan and vgchange 
> implemented in kernel and called at boot time ? This would make us be able to 
> consider logical volumes as standard partitions and mount them easily, even 
> as /

That's what an initrd/initramfs is for ;)

> 
> Thank you,
> Benoit.
> 
> PS: Please cc-me with the anser as I'm not subscribed to the list.
> 
> 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

-- 

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Heinz    -- The LVM Guy --

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Re: [linux-lvm] lvm metadata

[Luca Berra]

On Tue, Nov 11, 2003 at 11:44:36AM +0100, Benoit wrote:
>You may ask why. Then is my second question, why aren't vgscan and vgchange 
>implemented in kernel and called at boot time ? This would make us be able to 
>consider logical volumes as standard partitions and mount them easily, even 
>as /
because lvm tools are too big and complex to go into kernel space,
they are better into userspace and invoked via initrd if you want to
use lvm root.

L.

-- 
Luca Berra -- bluca@comedia.it
        Communication Media & Services S.r.l.
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Re: [linux-lvm] lvm metadata

[Benoit]

On Tuesday 11 November 2003 16:02, you wrote:
> On Tue, Nov 11, 2003 at 11:44:36AM +0100, Benoit wrote:
> > Hello,
> >
> > You may ask why. Then is my second question, why aren't vgscan and
> > vgchange implemented in kernel and called at boot time ? This would make
> > us be able to consider logical volumes as standard partitions and mount
> > them easily, even as /
>
> That's what an initrd/initramfs is for ;)

I think initrd is more a trick than the real place to do it. I mean, making a 
ramdisk needs of space, time to create it, and unnecessary initialisation 
things. This, only to do a vgscan, vgchange -a at boottime. Aren't those 
tools simple calls to system functions ?


> > PS: Please cc-me with the anser as I'm not subscribed to the list.

[linux-lvm] lvm metadata

[Pål Driveklepp]

[-- Attachment #1: Type: text/plain, Size: 2357 bytes --]

hi! i am truly desperate! i messed up my metadata and pvdisplay,
vgdisplay and lvdisplay outputs nothing. all my disks are still
functional and present. i keep getting the error message:

# vgcfgrestore -f main_disk_group_mod3 main_disk_group
 Cannot change metadata for partial volume group main_disk_group
 Restore failed.

i found almost no information about this error message on the web. i
have one backup-file that i am pretty sure is the one i want to backup
(see attachment). it seems /dev/sda's uuid has changed and that is why
i modified it to have the right uuid (hence the "vgcfgrestore -f
main_disk_group_mod3")

lvmdiskscan outputs the following:
  /dev/ram0      [       64.00 MB]
  /dev/sda       [      465.76 GB] LVM physical volume
  /dev/evms/hda1 [        8.99 GB]
  /dev/ram1      [       64.00 MB]
  /dev/hda1      [        8.99 GB]
  /dev/hdc1      [      232.88 GB] LVM physical volume
  /dev/evms/hda5 [      431.40 MB]
  /dev/ram2      [       64.00 MB]
  /dev/evms/hdb1 [      149.05 GB] LVM physical volume
  /dev/ram3      [       64.00 MB]
  /dev/evms/hdc1 [      232.88 GB] LVM physical volume
  /dev/ram4      [       64.00 MB]
  /dev/evms/hdd1 [      186.31 GB]
  /dev/ram5      [       64.00 MB]
  /dev/hda5      [      431.40 MB]
  /dev/ram6      [       64.00 MB]
  /dev/ram7      [       64.00 MB]
  /dev/ram8      [       64.00 MB]
  /dev/ram9      [       64.00 MB]
  /dev/ram10     [       64.00 MB]
  /dev/ram11     [       64.00 MB]
  /dev/ram12     [       64.00 MB]
  /dev/ram13     [       64.00 MB]
  /dev/ram14     [       64.00 MB]
  /dev/ram15     [       64.00 MB]
  /dev/sdb       [      465.76 GB] LVM physical volume
  /dev/hdb1      [      149.05 GB]
  /dev/hdd1      [      186.31 GB]
  0 disks
  23 partitions
  2 LVM physical volume whole disks
  3 LVM physical volumes

disk overview:
/dev/sdb	14AP4R-X75R-94Dx-Pk5g-HU0e-F6yh-8tQoEz	500gig	
(somehow changed to mQYVpB-CCAn-OdlL-Ows5-m33h-gCMy-DWS8ku)
/dev/hdb	kUgW4k-AO0G-qRS0-0cH8-VkzD-Xjfj-ZjzZVL	150gig
/dev/hdc1	JDMxOF-84VA-Ir6e-tAeB-LAKj-gy4J-7GXspF	250gig
/dev/sda	F87gox-1Z8e-eDcZ-QUxW-9gLI-XJLp-ySl017	500gig


Pål Driveklepp
Norway

>  But the error probably means you're attempting to use an incomplete backup
>  (or you attempted hand-editing it incorrectly).
>
>  Alasdair

[-- Attachment #2: main_disk_group_00001.vg --]
[-- Type: application/octet-stream, Size: 2156 bytes --]

# Generated by LVM2: Fri Apr 18 01:30:47 2008

contents = "Text Format Volume Group"
version = 1

description = "Created *before* executing 'vgreduce --removemissing main_disk_group'"

creation_host = "indigo"	# Linux indigo 2.6.20-16-generic #2 SMP Tue Feb 12 05:41:34 UTC 2008 i686
creation_time = 1208475047	# Fri Apr 18 01:30:47 2008

main_disk_group {
	id = "EaYeB6-uFHx-d2p2-TVFl-dyom-fQee-OxXbTF"
	seqno = 8
	status = ["RESIZEABLE", "PARTIAL", "READ"]
	extent_size = 8192		# 4 Megabytes
	max_lv = 0
	max_pv = 0

	physical_volumes {

		pv0 {
			id = "14AP4R-X75R-94Dx-Pk5g-HU0e-F6yh-8tQoEz"
			device = "/dev/sdb"	# Hint only

			status = ["ALLOCATABLE"]
			pe_start = 384
			pe_count = 119234	# 465.758 Gigabytes
		}

		pv1 {
			id = "kUgW4k-AO0G-qRS0-0cH8-VkzD-Xjfj-ZjzZVL"
			device = "unknown device"	# Hint only

			status = ["ALLOCATABLE"]
			pe_start = 384
			pe_count = 38156	# 149.047 Gigabytes
		}

		pv2 {
			id = "JDMxOF-84VA-Ir6e-tAeB-LAKj-gy4J-7GXspF"
			device = "/dev/hdc1"	# Hint only

			status = ["ALLOCATABLE"]
			pe_start = 384
			pe_count = 59618	# 232.883 Gigabytes
		}

		pv3 {
			id = "F87gox-1Z8e-eDcZ-QUxW-9gLI-XJLp-ySl017"
			device = "/dev/sda"	# Hint only

			status = ["ALLOCATABLE"]
			pe_start = 384
			pe_count = 119234	# 465.758 Gigabytes
		}
	}

	logical_volumes {

		diskarray {
			id = "KrYHQE-dQzy-mVsY-CmOj-rN37-O1X7-BD9Adb"
			status = ["READ", "WRITE", "VISIBLE"]
			segment_count = 4

			segment1 {
				start_extent = 0
				extent_count = 119234	# 465.758 Gigabytes

				type = "striped"
				stripe_count = 1	# linear

				stripes = [
					"pv0", 0
				]
			}
			segment2 {
				start_extent = 119234
				extent_count = 38156	# 149.047 Gigabytes

				type = "striped"
				stripe_count = 1	# linear

				stripes = [
					"pv1", 0
				]
			}
			segment3 {
				start_extent = 157390
				extent_count = 59618	# 232.883 Gigabytes

				type = "striped"
				stripe_count = 1	# linear

				stripes = [
					"pv2", 0
				]
			}
			segment4 {
				start_extent = 217008
				extent_count = 118537	# 463.035 Gigabytes

				type = "striped"
				stripe_count = 1	# linear

				stripes = [
					"pv3", 0
				]
			}
		}
	}
}

Re: [linux-lvm] lvm metadata

[Alasdair G Kergon]

If you hand-edited you might want to change
  status = ["RESIZEABLE", "PARTIAL", "READ"]
to
  status = ["RESIZEABLE", "READ", "WRITE"]

Alasdair
-- 
agk@redhat.com