[linux-lvm] how to access the partition on LV?

[linux-lvm] how to access the partition on LV?

[Ming Zhang]

I think this is a very common question but i can not find the answer.
any idea on how to access the partition on these lv since no device
node?


[root@fc3-i386-2 ~]# fdisk /dev/vg1/v1 -l

Disk /dev/vg1/v1: 469 MB, 469762048 bytes
255 heads, 63 sectors/track, 57 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

       Device Boot      Start         End      Blocks   Id  System
/dev/vg1/v1p1               1          13      104391   83  Linux
/dev/vg1/v1p2              14          57      353430   83  Linux

Thanks!

Ming

Re: [linux-lvm] how to access the partition on LV?

[AJ Lewis]

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On Thu, Jul 28, 2005 at 11:17:41AM -0400, Ming Zhang wrote:
> I think this is a very common question but i can not find the answer.
> any idea on how to access the partition on these lv since no device
> node?
> 
> 
> [root@fc3-i386-2 ~]# fdisk /dev/vg1/v1 -l
> 
> Disk /dev/vg1/v1: 469 MB, 469762048 bytes
> 255 heads, 63 sectors/track, 57 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> 
>        Device Boot      Start         End      Blocks   Id  System
> /dev/vg1/v1p1               1          13      104391   83  Linux
> /dev/vg1/v1p2              14          57      353430   83  Linux

You don't.  Don't put partition tables on LVs.  The whole point of using LVM
is you don't need to partition anymore, and your block devices can be dynamic.
If you another block devices, you lvcreate it.  If you don't have enough space
in your VG, you add a PV to it, then lvcreate the new block device.  Have you
read through the HOWTO referenced below?

-- 
AJ Lewis                                   Voice:  612-638-0500
Red Hat                                    E-Mail: alewis@redhat.com
One Main Street SE, Suite 209
Minneapolis, MN 55414
   
Current GPG fingerprint = D9F8 EDCE 4242 855F A03D  9B63 F50C 54A8 578C 8715
Grab the key at: http://people.redhat.com/alewis/gpg.html or one of the
many keyservers out there...


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Re: [linux-lvm] how to access the partition on LV?

[Ming Zhang]

On Thu, 2005-07-28 at 11:45 -0500, AJ Lewis wrote:
> On Thu, Jul 28, 2005 at 11:17:41AM -0400, Ming Zhang wrote:
> > I think this is a very common question but i can not find the answer.
> > any idea on how to access the partition on these lv since no device
> > node?
> > 
> > 
> > [root@fc3-i386-2 ~]# fdisk /dev/vg1/v1 -l
> > 
> > Disk /dev/vg1/v1: 469 MB, 469762048 bytes
> > 255 heads, 63 sectors/track, 57 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> > 
> >        Device Boot      Start         End      Blocks   Id  System
> > /dev/vg1/v1p1               1          13      104391   83  Linux
> > /dev/vg1/v1p2              14          57      353430   83  Linux
> 

the problem is that we export a LV via iscsi to a remote box and become
a scsi disk. so it is partitioned and utilized. then it does have
partition on it. even it is exported to a linux box, u possibly will
use /dev/sdx1 instead of directly use /dev/sdx, rite?

> You don't.  Don't put partition tables on LVs.  The whole point of using LVM
> is you don't need to partition anymore, and your block devices can be dynamic.
> If you another block devices, you lvcreate it.  If you don't have enough space
> in your VG, you add a PV to it, then lvcreate the new block device.  Have you
> read through the HOWTO referenced below?

i can not see this HOWTO, where u referenced it?

thx!

ming

> 

Re: [linux-lvm] how to access the partition on LV?

[AJ Lewis]

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On Thu, Jul 28, 2005 at 01:13:50PM -0400, Ming Zhang wrote:
> On Thu, 2005-07-28 at 11:45 -0500, AJ Lewis wrote:
> > On Thu, Jul 28, 2005 at 11:17:41AM -0400, Ming Zhang wrote:
> > > I think this is a very common question but i can not find the answer.
> > > any idea on how to access the partition on these lv since no device
> > > node?
> > > 
> > > 
> > > [root@fc3-i386-2 ~]# fdisk /dev/vg1/v1 -l
> > > 
> > > Disk /dev/vg1/v1: 469 MB, 469762048 bytes
> > > 255 heads, 63 sectors/track, 57 cylinders
> > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > 
> > >        Device Boot      Start         End      Blocks   Id  System
> > > /dev/vg1/v1p1               1          13      104391   83  Linux
> > > /dev/vg1/v1p2              14          57      353430   83  Linux
> > 
> 
> the problem is that we export a LV via iscsi to a remote box and become
> a scsi disk. so it is partitioned and utilized. then it does have
> partition on it. even it is exported to a linux box, u possibly will
> use /dev/sdx1 instead of directly use /dev/sdx, rite?

Ahh - I see.  Well, on the node exporting the LVs, you don't access it.  I
dunno if kpartx or some other partitioning tool could do it - it might.  But
as far as the standard partion handling code goes, LVs don't exist.  I know
why you're doing it this way - I don't know why you want to access the
partitions on the exporting (target) node.  Do you really need to?
 
> > You don't.  Don't put partition tables on LVs.  The whole point of using
> > LVM is you don't need to partition anymore, and your block devices can be
> > dynamic.  If you another block devices, you lvcreate it.  If you don't
> > have enough space in your VG, you add a PV to it, then lvcreate the new
> > block device.  Have you read through the HOWTO referenced below?
> 
> i can not see this HOWTO, where u referenced it?

It's at the bottom of all messages that go to the linux-lvm ML -
http://tldp.org/HOWTO/LVM-HOWTO/ 
-- 
AJ Lewis                                   Voice:  612-638-0500
Red Hat                                    E-Mail: alewis@redhat.com
One Main Street SE, Suite 209
Minneapolis, MN 55414
   
Current GPG fingerprint = D9F8 EDCE 4242 855F A03D  9B63 F50C 54A8 578C 8715
Grab the key at: http://people.redhat.com/alewis/gpg.html or one of the
many keyservers out there...


[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: [linux-lvm] how to access the partition on LV?

[Ming Zhang]

On Thu, 2005-07-28 at 12:32 -0500, AJ Lewis wrote:
> On Thu, Jul 28, 2005 at 01:13:50PM -0400, Ming Zhang wrote:
> > On Thu, 2005-07-28 at 11:45 -0500, AJ Lewis wrote:
> > > On Thu, Jul 28, 2005 at 11:17:41AM -0400, Ming Zhang wrote:
> > > > I think this is a very common question but i can not find the answer.
> > > > any idea on how to access the partition on these lv since no device
> > > > node?
> > > > 
> > > > 
> > > > [root@fc3-i386-2 ~]# fdisk /dev/vg1/v1 -l
> > > > 
> > > > Disk /dev/vg1/v1: 469 MB, 469762048 bytes
> > > > 255 heads, 63 sectors/track, 57 cylinders
> > > > Units = cylinders of 16065 * 512 = 8225280 bytes
> > > > 
> > > >        Device Boot      Start         End      Blocks   Id  System
> > > > /dev/vg1/v1p1               1          13      104391   83  Linux
> > > > /dev/vg1/v1p2              14          57      353430   83  Linux
> > > 
> > 
> > the problem is that we export a LV via iscsi to a remote box and become
> > a scsi disk. so it is partitioned and utilized. then it does have
> > partition on it. even it is exported to a linux box, u possibly will
> > use /dev/sdx1 instead of directly use /dev/sdx, rite?
> 
> Ahh - I see.  Well, on the node exporting the LVs, you don't access it.  I
> dunno if kpartx or some other partitioning tool could do it - it might.  But
> as far as the standard partion handling code goes, LVs don't exist.  I know
> why you're doing it this way - I don't know why you want to access the
> partitions on the exporting (target) node.  Do you really need to?
yes, i guess that is the only solution. we have end users want that
feature. so i think a work around is to run a iscsi initiator at local
site and access via iscsi again.


>  
> > > You don't.  Don't put partition tables on LVs.  The whole point of using
> > > LVM is you don't need to partition anymore, and your block devices can be
> > > dynamic.  If you another block devices, you lvcreate it.  If you don't
> > > have enough space in your VG, you add a PV to it, then lvcreate the new
> > > block device.  Have you read through the HOWTO referenced below?
> > 
> > i can not see this HOWTO, where u referenced it?
> 
> It's at the bottom of all messages that go to the linux-lvm ML -
> http://tldp.org/HOWTO/LVM-HOWTO/ 

i guess this is because i got the email from u directly. so lvm list
will not send to me again. and only email via it will have that link. i
checked my archival and all emails via lvm list has that.

Re: [linux-lvm] how to access the partition on LV?

[AJ Lewis]

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On Thu, Jul 28, 2005 at 01:42:10PM -0400, Ming Zhang wrote:
> On Thu, 2005-07-28 at 12:32 -0500, AJ Lewis wrote:
> > On Thu, Jul 28, 2005 at 01:13:50PM -0400, Ming Zhang wrote:
> > > the problem is that we export a LV via iscsi to a remote box and become
> > > a scsi disk. so it is partitioned and utilized. then it does have
> > > partition on it. even it is exported to a linux box, u possibly will
> > > use /dev/sdx1 instead of directly use /dev/sdx, rite?
> > 
> > Ahh - I see.  Well, on the node exporting the LVs, you don't access it.  I
> > dunno if kpartx or some other partitioning tool could do it - it might.  But
> > as far as the standard partion handling code goes, LVs don't exist.  I know
> > why you're doing it this way - I don't know why you want to access the
> > partitions on the exporting (target) node.  Do you really need to?
> yes, i guess that is the only solution. we have end users want that
> feature. so i think a work around is to run a iscsi initiator at local
> site and access via iscsi again.

Could play with loopback devices too if you need to do it on the target - that
might get nasty quickly though.
 
> > > i can not see this HOWTO, where u referenced it?
> > 
> > It's at the bottom of all messages that go to the linux-lvm ML -
> > http://tldp.org/HOWTO/LVM-HOWTO/ 
> 
> i guess this is because i got the email from u directly. so lvm list
> will not send to me again. and only email via it will have that link. i
> checked my archival and all emails via lvm list has that.

Heh - yep, that'd do it ;) 

-- 
AJ Lewis                                   Voice:  612-638-0500
Red Hat                                    E-Mail: alewis@redhat.com
One Main Street SE, Suite 209
Minneapolis, MN 55414
   
Current GPG fingerprint = D9F8 EDCE 4242 855F A03D  9B63 F50C 54A8 578C 8715
Grab the key at: http://people.redhat.com/alewis/gpg.html or one of the
many keyservers out there...


[-- Attachment #2: Type: application/pgp-signature, Size: 189 bytes --]

Re: [linux-lvm] how to access the partition on LV?

[Ming Zhang]

On Thu, 2005-07-28 at 13:03 -0500, AJ Lewis wrote:
> On Thu, Jul 28, 2005 at 01:42:10PM -0400, Ming Zhang wrote:
> > On Thu, 2005-07-28 at 12:32 -0500, AJ Lewis wrote:
> > > On Thu, Jul 28, 2005 at 01:13:50PM -0400, Ming Zhang wrote:
> > > > the problem is that we export a LV via iscsi to a remote box and become
> > > > a scsi disk. so it is partitioned and utilized. then it does have
> > > > partition on it. even it is exported to a linux box, u possibly will
> > > > use /dev/sdx1 instead of directly use /dev/sdx, rite?
> > > 
> > > Ahh - I see.  Well, on the node exporting the LVs, you don't access it.  I
> > > dunno if kpartx or some other partitioning tool could do it - it might.  But
> > > as far as the standard partion handling code goes, LVs don't exist.  I know
> > > why you're doing it this way - I don't know why you want to access the
> > > partitions on the exporting (target) node.  Do you really need to?
> > yes, i guess that is the only solution. we have end users want that
> > feature. so i think a work around is to run a iscsi initiator at local
> > site and access via iscsi again.
> 
> Could play with loopback devices too if you need to do it on the target - that
> might get nasty quickly though.
can loopback support partition? might worthy a try. :P

>  
> > > > i can not see this HOWTO, where u referenced it?
> > > 
> > > It's at the bottom of all messages that go to the linux-lvm ML -
> > > http://tldp.org/HOWTO/LVM-HOWTO/ 
> > 
> > i guess this is because i got the email from u directly. so lvm list
> > will not send to me again. and only email via it will have that link. i
> > checked my archival and all emails via lvm list has that.
> 
> Heh - yep, that'd do it ;) 
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

this time works. :P

Re: [linux-lvm] how to access the partition on LV?

[Alasdair G Kergon]

> > the problem is that we export a LV via iscsi to a remote box and become
> > a scsi disk. so it is partitioned and utilized. then it does have
> > partition on it. even it is exported to a linux box, u possibly will
> > use /dev/sdx1 instead of directly use /dev/sdx, rite?
 
> dunno if kpartx or some other partitioning tool could do it

Give kpartx a try. It reads a dos partition table and creates partitions
using device-mapper.

You'll find kpartx in multipath-tools (device-mapper-multipath package on Red Hat).
  ftp://sources.redhat.com/pub/dm/multipath-tools/multipath-tools-0.4.5.48.tgz

Alasdair
-- 
agk@redhat.com

Re: [linux-lvm] how to access the partition on LV?

[Ming Zhang]

thx.

ming

On Fri, 2005-07-29 at 21:56 +0100, Alasdair G Kergon wrote:
> > > the problem is that we export a LV via iscsi to a remote box and become
> > > a scsi disk. so it is partitioned and utilized. then it does have
> > > partition on it. even it is exported to a linux box, u possibly will
> > > use /dev/sdx1 instead of directly use /dev/sdx, rite?
>  
> > dunno if kpartx or some other partitioning tool could do it
> 
> Give kpartx a try. It reads a dos partition table and creates partitions
> using device-mapper.
> 
> You'll find kpartx in multipath-tools (device-mapper-multipath package on Red Hat).
>   ftp://sources.redhat.com/pub/dm/multipath-tools/multipath-tools-0.4.5.48.tgz
> 
> Alasdair