[linux-lvm] Adding a disk to expand an existing logical volume

[linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

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Howdy,

 

 

I have a live production system w/ logical volume that i want to add a drive
to. I just wanted to confirm that adding a drive
(fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
a disk to logical volumes? I want to ensure that the existing data on the
logical volume isn't compromised and have never done this before.

 

If theres something I should be aware of or if my process is incorrect,
please let me know. Any help is extremely appreciated J 

 

 

Thanks,

 

Kevin

 


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Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Digimer]

On 10-05-19 11:43 AM, kevin wrote:
> Howdy,
>
> (fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding

The mkfs isn't supposed to be there, just set the new drive's partition 
to type '8e' (Linux LVM).

-- 
Digimer
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Re: [linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

>The mkfs isn't supposed to be there, just set the new drive's partition 
>to type '8e' (Linux LVM).

Thanks for the quick response. So to recap, for a 144gb drive (/dev/sda1) :

1. fdisk /dev/sda1 type 8e

2. pvcreate /dev/sda1

3. vgextend existing_group_name /dev/sda1

4. lvextend -L+144G /dev/VolGroup00/existing_group_name



Does that look correct?


Thanks so much once again,


Kevin 
http://blog.stardothosting.com

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Digimer]

On 10-05-19 12:09 PM, kevin wrote:
>> The mkfs isn't supposed to be there, just set the new drive's partition
>> to type '8e' (Linux LVM).
>
> Thanks for the quick response. So to recap, for a 144gb drive (/dev/sda1) :
>
> 1. fdisk /dev/sda1 type 8e
> 2. pvcreate /dev/sda1
> 3. vgextend existing_group_name /dev/sda1
> 4. lvextend -L+144G /dev/VolGroup00/existing_group_name
>
> Does that look correct?
>
> Thanks so much once again,
>
> Kevin

Hi Kevin,

   I've been meaning to add this process to my wiki for a while now. 
This is as good a time as any, so take a gander here:

http://wiki.alteeve.com/index.php/Adding_Space_to_an_LVM

   Note that it's a copy-pasted from some of my other docs, so some of 
it will reference non-existing things, but the steps should all be there.

-- 
Digimer
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Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Michael Guntsche]

On 2010.05.19 11:58:03 , Digimer wrote:
> On 10-05-19 11:43 AM, kevin wrote:
> >Howdy,
> >
> >(fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
> 
> The mkfs isn't supposed to be there, just set the new drive's
> partition to type '8e' (Linux LVM).
Or use the full device without any partition at all.

/Michael

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Ron Johnson]

On 05/19/2010 11:24 AM, Michael Guntsche wrote:
> On 2010.05.19 11:58:03 , Digimer wrote:
>> On 10-05-19 11:43 AM, kevin wrote:
>>> Howdy,
>>>
>>> (fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
>>
>> The mkfs isn't supposed to be there, just set the new drive's
>> partition to type '8e' (Linux LVM).
> Or use the full device without any partition at all.
>

I wonder if this will have any adverse affects on drives with 4KB 
sectors?

-- 
Dissent is patriotic, remember?

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Luca Berra]

On Wed, May 19, 2010 at 05:28:28PM -0500, Ron Johnson wrote:
> On 05/19/2010 11:24 AM, Michael Guntsche wrote:
>> On 2010.05.19 11:58:03 , Digimer wrote:
>>> On 10-05-19 11:43 AM, kevin wrote:
>>>> Howdy,
>>>>
>>>> (fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
>>>
>>> The mkfs isn't supposed to be there, just set the new drive's
>>> partition to type '8e' (Linux LVM).
>> Or use the full device without any partition at all.
>>
>
> I wonder if this will have any adverse affects on drives with 4KB sectors?
it depends
on a disk with 4k sector, using the whole device is more likely to have
a correct alignment (0 is a multiple of 4k)

on a disk with 4k sector and the first sector shifted (some drives have
a jumper to achieve this, it might be called something like "XP
compatibility") using the whole device, or anything not aligned to
63x512byte will result in unaligned data.

afair recent kernels should expose the alignment and sector size under
/sys/block/..., (if the drive exposes that info and does not lie, that
is.) and fdisk/parted/lvm/md should correctly align data start.

On a personal note, i really despise partition tables, it is a broken
design from the early eighties, we should be able to move on. If you
must use a GPT partition, at least it has a backup block.

L.


-- 
Luca Berra -- bluca@comedia.it
         Communication Media & Services S.r.l.
  /"\
  \ /     ASCII RIBBON CAMPAIGN
   X        AGAINST HTML MAIL
  / \

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Bryn M. Reeves]

On 05/19/2010 11:28 PM, Ron Johnson wrote:
> On 05/19/2010 11:24 AM, Michael Guntsche wrote:
>> On 2010.05.19 11:58:03 , Digimer wrote:
>>> On 10-05-19 11:43 AM, kevin wrote:
>>>> Howdy,
>>>>
>>>> (fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
>>>
>>> The mkfs isn't supposed to be there, just set the new drive's
>>> partition to type '8e' (Linux LVM).
>> Or use the full device without any partition at all.
>>
> 
> I wonder if this will have any adverse affects on drives with 4KB 
> sectors?
> 

Not really, if anything it simplifies getting correct alignment for the
data region of the PV.

Regards,
Bryn.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Malahal Naineni]

Digimer [linux@alteeve.com] wrote:
> On 10-05-19 11:43 AM, kevin wrote:
> >Howdy,
> >
> >(fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
> 
> The mkfs isn't supposed to be there, just set the new drive's
> partition to type '8e' (Linux LVM).

If I were you, I would not bother with partition(s). I will add the
whole disk to LVM.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

>If I were you, I would not bother with partition(s). I will add the
>whole disk to LVM.


I intend for the entire disk to be used -- so I should just skip the fdisk
step?



Thanks,


Kevin
http://blog.stardothosting.com

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Digimer]

On 10-05-19 12:37 PM, kevin wrote:
>
>> If I were you, I would not bother with partition(s). I will add the
>> whole disk to LVM.
>
>
> I intend for the entire disk to be used -- so I should just skip the fdisk
> step?
>
>
>
> Thanks,
>
>
> Kevin
> http://blog.stardothosting.com

Unless Malahal knows something I don't (which is always possible), then 
you still need to create a single partition that consumes the whole disk 
and then assign that to you VG.

-- 
Digimer
E-Mail:         linux@alteeve.com
AN!Whitepapers: http://alteeve.com
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Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Bryn M. Reeves]

On 05/19/2010 05:46 PM, Digimer wrote:
> On 10-05-19 12:37 PM, kevin wrote:
>>
>>> If I were you, I would not bother with partition(s). I will add the
>>> whole disk to LVM.
>>
>>
>> I intend for the entire disk to be used -- so I should just skip the fdisk
>> step?
>>
>>
>>
>> Thanks,
>>
>>
>> Kevin
>> http://blog.stardothosting.com
> 
> Unless Malahal knows something I don't (which is always possible), then 
> you still need to create a single partition that consumes the whole disk 
> and then assign that to you VG.
> 

Running pvcreate on a whole disk works just fine.

Regards,
Bryn.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Stuart D. Gathman]

On Wed, 19 May 2010, kevin wrote:

> >If I were you, I would not bother with partition(s). I will add the
> >whole disk to LVM.
> 
> I intend for the entire disk to be used -- so I should just skip the fdisk
> step?

Yes, just do the pvcreate directly on /dev/sdc (instead of /dev/sdc1).

I would only recommend this if the drive is permanently attached to your
server.  If there is any possibility of it getting moved to another system,
especially another OS, it is likely to appear "unformatted" and the other
OS will offer to create a partition table, etc, destroying the data.
The partition table, although otherwise useless for LVM (and a pain when
trying to align PPs to some lower lever boundary), does serve the purpose
of telling other PC operating systems that there is something there.

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Digimer]

On 10-05-19 12:51 PM, Stuart D. Gathman wrote:
> On Wed, 19 May 2010, kevin wrote:
>
>>> If I were you, I would not bother with partition(s). I will add the
>>> whole disk to LVM.
>>
>> I intend for the entire disk to be used -- so I should just skip the fdisk
>> step?
>
> Yes, just do the pvcreate directly on /dev/sdc (instead of /dev/sdc1).
>
> I would only recommend this if the drive is permanently attached to your
> server.  If there is any possibility of it getting moved to another system,
> especially another OS, it is likely to appear "unformatted" and the other
> OS will offer to create a partition table, etc, destroying the data.
> The partition table, although otherwise useless for LVM (and a pain when
> trying to align PPs to some lower lever boundary), does serve the purpose
> of telling other PC operating systems that there is something there.

There ya go, I learn something new every day. :)

-- 
Digimer
E-Mail:         linux@alteeve.com
AN!Whitepapers: http://alteeve.com
Node Assassin:  http://nodeassassin.org

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

> I would only recommend this if the drive is permanently attached to your
> server.  If there is any possibility of it getting moved to another
system,
> especially another OS, it is likely to appear "unformatted" and the other
> OS will offer to create a partition table, etc, destroying the data.
> The partition table, although otherwise useless for LVM (and a pain when
> trying to align PPs to some lower lever boundary), does serve the purpose
> of telling other PC operating systems that there is something there.

This drive is to be permanently attached to the system so I don't think I
need to worry about marking it as 8e in fdisk. Thanks all for your help.
This clarifies a lot of things for me.


~k

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

One last thing I want to confirm is the lvextend command to 'grow' the
logical volume :


lvextend -L+144G /dev/VolGroup00/my_volume 

After all said steps in previous messages on this thread are complete, is
the above command correct for my particular scenario? Do I want to 'extend'
the volume size or 'grow' it?

Not sure what the difference is.


~k

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Richard Shaw]

On Wed, May 19, 2010 at 12:09 PM, kevin <k@kevinkevin.com> wrote:
> One last thing I want to confirm is the lvextend command to 'grow' the
> logical volume :
>
>
> lvextend -L+144G /dev/VolGroup00/my_volume
>
> After all said steps in previous messages on this thread are complete, is
> the above command correct for my particular scenario? Do I want to 'extend'
> the volume size or 'grow' it?
>
> Not sure what the difference is.

Chiming in a little late here but I would suggest the following
(although I'm certainly not a LVM expert):

lvextend -l +100%FREE /dev/VolGroup00/my_volume (notice the lower case
l in -l, not upper)

This should make sure you add 100% of the extents of the new drive to
your logical volume. As I've said, I'm not an expert so I don't know
the innards of "lvextend" but I would be concerned that if you specify
the size of the expansion in gigabytes instead of as a percentage that
you might get some unallocated extents due to rounding.

Richard

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Ray Morris]

> lvextend -L+144G /dev/VolGroup00/my_volume

    If you want to use all available space:

lvextend -L+100%FREE /dev/VolGroup00/my_volume


> I should note that this is a logical volume for a
> collection of Xen virtualized environments so its
> not an actual EXT3 filesystem. I wouldn’t need to
> run the last step I imagine.

   Typically Xen images are files on the filesystem
of the host, so yes, you'd need to resize the host
filesystem, if you are creating Xen image files. Howver,
as long as you are making changes to your LVM, there is
another way which we use, because we think it's better.
Rather than having one huge LV which contains files which
are accessed as though they were block devices, we create
a LV for each guest.  If you have only one big LV, that's
kind of pointless indirection, overhead that gains you
nothing.  It's also problematic for recovery because
you have multiple overlapping ext3 filesystems - one
inside the other, meaning that recovery utilities will
find bogus superblocks belonging to the wrong filesystem.
--
Ray Morris
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On 05/19/2010 12:09:48 PM, kevin wrote:
> One last thing I want to confirm is the lvextend command to 'grow' the
> logical volume :
> 
> 
> lvextend -L+144G /dev/VolGroup00/my_volume
> 
> After all said steps in previous messages on this thread are  
> complete, is
> the above command correct for my particular scenario? Do I want to  
> 'extend'
> the volume size or 'grow' it?
> 
> Not sure what the difference is.
> 
> 
> ~k
> 
> 
> _______________________________________________
> 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/
> 
> 

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Digimer]

On 10-05-19 01:35 PM, Ray Morris wrote:
>> lvextend -L+144G /dev/VolGroup00/my_volume
>
> If you want to use all available space:
>
> lvextend -L+100%FREE /dev/VolGroup00/my_volume

As Richard pointed out, using '+100%FREE' calls for the small 'l', not 
L. The capital L is used when specifying a fixed size.

-- 
Digimer
E-Mail:         linux@alteeve.com
AN!Whitepapers: http://alteeve.com
Node Assassin:  http://nodeassassin.org

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Ray Morris]

>> The partition table, although otherwise useless for LVM (and a pain  
>> when
>> trying to align PPs to some lower lever boundary), does serve the  
>> purpose
>> of telling other PC operating systems that there is something there.

   It's also useful during the boot process.  If, for example, you
later add another disk, this disk might become sdd, where it used to
be sdc.  That can confuse initrd and friends and result in an
unbootable system.  On almost every machine where I've skipped
creating partitions for RAID or LVM, this kind of thing has come
back to bite me later - maybe years later.  Now, I always create
"Linux LVM" partitions for LVM and "Linux raid autodetect" partitions
for RAID.  It makes booting an recovering much more reliable in
case of changes or problems.

>  a pain when trying to align PPs to some lower lever boundary

    A trick to avoid all of the math of alignment is to just
start the first partition on sector 512 every time, rather
than sector 63.  Sometimes you can save a few KB by doing the
math and finding a lower offset,  but it's just a few KB -
who cares.  That works because 512 sectors is 256KB - a
perfect multiple of any RAID size you might use.
--
Ray Morris
support@bettercgi.com

Strongbox - The next generation in site security:
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On 05/19/2010 11:57:40 AM, Digimer wrote:
> On 10-05-19 12:51 PM, Stuart D. Gathman wrote:
>> On Wed, 19 May 2010, kevin wrote:
>> 
>>>> If I were you, I would not bother with partition(s). I will add the
>>>> whole disk to LVM.
>>> 
>>> I intend for the entire disk to be used -- so I should just skip  
>>> the fdisk
>>> step?
>> 
>> Yes, just do the pvcreate directly on /dev/sdc (instead of  
>> /dev/sdc1).
>> 
>> I would only recommend this if the drive is permanently attached to  
>> your
>> server.  If there is any possibility of it getting moved to another  
>> system,
>> especially another OS, it is likely to appear "unformatted" and the  
>> other
>> OS will offer to create a partition table, etc, destroying the data.
>> The partition table, although otherwise useless for LVM (and a pain  
>> when
>> trying to align PPs to some lower lever boundary), does serve the  
>> purpose
>> of telling other PC operating systems that there is something there.
> 
> There ya go, I learn something new every day. :)
> 
>-- 
> Digimer
> E-Mail:         linux@alteeve.com
> AN!Whitepapers: http://alteeve.com
> Node Assassin:  http://nodeassassin.org
> 
> _______________________________________________
> 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/
> 

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Stuart D. Gathman]

On Wed, 19 May 2010, Ray Morris wrote:

>  It's also useful during the boot process.  If, for example, you
> later add another disk, this disk might become sdd, where it used to
> be sdc.  That can confuse initrd and friends and result in an
> unbootable system.  On almost every machine where I've skipped
> creating partitions for RAID or LVM, this kind of thing has come
> back to bite me later - maybe years later.  Now, I always create
> "Linux LVM" partitions for LVM and "Linux raid autodetect" partitions
> for RAID.  It makes booting an recovering much more reliable in
> case of changes or problems.

PVs are identified by UUID.  It doesn't matter whether they change
names.  And changing names from sdc1 to sdd1 is just as bad as changing
names from sdc to sdd. 

However, you are correct that the default device searching rules used by
lvm might work correctly with a Linux LVM labeled partition where they might
otherwise skip a device.  If you aren't familiar with lvm.conf, then
using labeled partitions is a safer course.  (initrd uses a copy
of lvm.conf to find PVs so it can activate the volume group of the
root filesystem if necessary.)

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Ray Morris]

>  If you aren't familiar with lvm.conf, then using labeled partitions
> is a safer course.  (initrd uses a copy of lvm.conf to find PVs so it
> can activate the volume group of the root filesystem if necessary.)

   Perhaps my point was obscured by my other text, so I'll highlight it:

> > It makes booting an recovering much more reliable in case of
> > changes or problems.

   Agreed, if all the devices are listed in lvm.conf, mdadm.conf,
etc. and nothing changes or has any problems then whole devices
work fine.  As long as all of the configuration files list everything
and initrd knows about any changes.  It's when something's not exactly
how it was originally configured that it's really handy for raid devices
to be marked as such by using partition type "fd", LVM devices to be
marked as such by using partition type "8e", etc.  That's been my
experience.  Your experience may differ, but that's my experience
from dealing with a lot of "won't boot" situations.

   Having said that, if you use partitions it's important that
the partition types not be WRONG.  I once spent far too long
trying to figure out why my devices were undetected.  It turned
out a RAID or LVM partition was marked with the default "83".
--
Ray Morris
support@bettercgi.com

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On 05/19/2010 02:34:38 PM, Stuart D. Gathman wrote:
> On Wed, 19 May 2010, Ray Morris wrote:
> 
> >  It's also useful during the boot process.  If, for example, you
> > later add another disk, this disk might become sdd, where it used to
> > be sdc.  That can confuse initrd and friends and result in an
> > unbootable system.  On almost every machine where I've skipped
> > creating partitions for RAID or LVM, this kind of thing has come
> > back to bite me later - maybe years later.  Now, I always create
> > "Linux LVM" partitions for LVM and "Linux raid autodetect"  
> partitions
> > for RAID.  It makes booting an recovering much more reliable in
> > case of changes or problems.
> 
> PVs are identified by UUID.  It doesn't matter whether they change
> names.  And changing names from sdc1 to sdd1 is just as bad as  
> changing
> names from sdc to sdd.
> 
> However, you are correct that the default device searching rules used  
> by
> lvm might work correctly with a Linux LVM labeled partition where  
> they might
> otherwise skip a device.  If you aren't familiar with lvm.conf, then
> using labeled partitions is a safer course.  (initrd uses a copy
> of lvm.conf to find PVs so it can activate the volume group of the
> root filesystem if necessary.)
> 
> --
> 	      Stuart D. Gathman <stuart@bmsi.com>
>     Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703  
> 591-6154
> "Confutatis maledictis, flammis acribus addictis" - background song  
> for
> a Microsoft sponsored "Where do you want to go from here?" commercial.
> 
> _______________________________________________
> 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/
> 
> 

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Bryn M. Reeves]

On 05/19/2010 05:37 PM, kevin wrote:
> 
>> If I were you, I would not bother with partition(s). I will add the
>> whole disk to LVM.
> 
> 
> I intend for the entire disk to be used -- so I should just skip the fdisk
> step?

You can either create a partition that spans the entire disk or create
the PV directly on the whole-disk device.

Both approaches have their advantages; with a partition table you are
less likely to run into problems with (buggy) software that assumes the
disks are "unformatted" because they do not contain an MBR-format
partition table and handily initialises them for you. On the other hand
it's somewhat easier (at least with older tools) to get alignment
constraints right when creating things on the bare disk (although you
still need to make sure that the start of the data area of the PV is
aligned properly if you want to get the best performance).

Regards,
Bryn.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Richard Jerrido]

On Wed, May 19, 2010 at 11:43 AM, kevin <k@kevinkevin.com> wrote:
> Howdy,
>
>
>
>
>
> I have a live production system w/ logical volume that i want to add a drive
> to. I just wanted to confirm that adding a drive
> (fdisk+mkfs+pvcreate+vgextend+lvextend) is the right way to go about adding
> a disk to logical volumes? I want to ensure that the existing data on the
> logical volume isn’t compromised and have never done this before.
>
>
>
> If theres something I should be aware of or if my process is incorrect,
> please let me know. Any help is extremely appreciated J
>
>
>
>
>
> Thanks,
>
>
>
> Kevin
>
>
>
> _______________________________________________
> 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/
>

The "mkfs" step isnt needed if you are expanding an existing logical
volume. A revised procedure would be the following:

- Add disk to system
- Partition it via fdisk. Set partition type to 8e (Linux LVM)
- run pvcreate initialize the partition for LVM
- run vgextend to expand your existing volume group with the new device.
- run lvextend to grow your logical volume.
- finally, run resize2fs (assuming you are using ext3/4) to grow the
file system.

Rich

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[kevin]

> - Add disk to system
> - Partition it via fdisk. Set partition type to 8e (Linux LVM)
> - run pvcreate initialize the partition for LVM
> - run vgextend to expand your existing volume group with the new device.
> - run lvextend to grow your logical volume.
> - finally, run resize2fs (assuming you are using ext3/4) to grow the
> file system.
>
>Rich


I should note that this is a logical volume for a collection of Xen virtualized environments so its not an actual EXT3 filesystem. I wouldn’t need to run the last step I imagine.

Re: [linux-lvm] Adding a disk to expand an existing logical volume

[Stuart D. Gathman]

On Wed, 19 May 2010, kevin wrote:

> a disk to logical volumes? I want to ensure that the existing data on the
> logical volume isn't compromised and have never done this before.
> 
> If theres something I should be aware of or if my process is incorrect,
> please let me know. Any help is extremely appreciated J 

While others have given you the procedure, I'll be the killjoy and point
out that the reliability of the VG as a whole goes down with additional
drives - unless you incorporate some kind of RAID.  For instance, if the
uptime ratio of a single drive is .99999 (5 sigmas), the uptime
of the system with two such drives is .99998.  

This is not so bad with just 2 drives (even 2 sigmas gives you .99^2 == .98),
but is something to keep in mind before adding the 3rd.   I prefer software
RAID1, it provides a lot of flexibility including "cloning" a drive by simply
removing it and is simple.  Other configurations will provide better
performance.

-- 
	      Stuart D. Gathman <stuart@bmsi.com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flammis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.