[linux-lvm] cannot extend lv

[linux-lvm] cannot extend lv

[Rainer.Lay]

I have a vg (data) with four drives /dev/sd[b-e]1
I created a 2 stripes lv (data1) with sd[bc]1
Now I want to add the remaining two drives to the lv, but lvextend 
complains about missing pes! I tried also with a very small number of 
pes - without success:

lvextend -l +400 /dev/data/data1 /dev/sde1 /dev/sdd1
lvextend -- extending logical volume "/dev/data/data1" to 35.45 GB
lvextend -- not enough free/allocatable physical extents to extend 
logical volume "/dev/data/data1"

It returns error code 12:
12 error setting up VGDA for logical volume extension
which is not very useful in this case.

Any idea?


kind regards,

Rainer


here comes a vgdisplay:
vgdisplay -v
--- Volume group ---
VG Name               data
VG Access             read/write
VG Status             available/resizable
VG #                  0
MAX LV                256
Cur LV                1
Open LV               1
MAX LV Size           255.99 GB
Max PV                256
Cur PV                4
Act PV                4
VG Size               50.83 GB
PE Size               4 MB
Total PE              13012
Alloc PE / Size       8676 / 33.89 GB
Free  PE / Size       4336 / 16.94 GB
VG UUID               sIKhBA-LMrL-e0h0-5NEt-mVSZ-3SrM-2KB7XS

--- Logical volume ---
LV Name                /dev/data/data1
VG Name                data
LV Write Access        read/write
LV Status              available
LV #                   1
# open                 2
LV Size                33.89 GB
Current LE             8676
Allocated LE           8676
Stripes                2
Stripe size (KByte)    16
Allocation             next free
Read ahead sectors     1024
Block device           58:0


--- Physical volumes ---
PV Name (#)           /dev/sdb1 (3)
PV Status             available / allocatable
Total PE / Free PE    4338 / 0

PV Name (#)           /dev/sdc1 (2)
PV Status             available / allocatable
Total PE / Free PE    4338 / 0

PV Name (#)           /dev/sdd1 (1)
PV Status             available / allocatable
Total PE / Free PE    2167 / 2167

PV Name (#)           /dev/sde1 (4)
PV Status             available / allocatable
Total PE / Free PE    2169 / 2169

Re: [linux-lvm] cannot extend lv

[idsfa]

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On Sat, Jan 18, 2003 at 11:35:28AM +0000,
Rainer.Lay@informatik.uni-erlangen.de wrote:

> I have a vg (data) with four drives /dev/sd[b-e]1
> I created a 2 stripes lv (data1) with sd[bc]1
                ^^^^^^^

You cannot extend striped lvs onto new pvs. Even on the
same physical hardware.  Once you have striped it, you are
tied to the pvs used.

If you think about it, this makes sense, as otherwise you
have some stripes containing more data than others.  In fact,
as soon as the smallest pv is full, you will not be able to
extend the lv, even if there is room in the other pvs.

If you want to have the filesystem striped over all the disks, you
will need to create a new lv which is striped across them all,
transfer the data to it, delete the old lv and then extend the
new one.

Backups highly recommended.

Michael

-- 
Think Locally, Act Globally:  
"It's cold in here ... I'd better release a few million tons of CFCs!"

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Re: [linux-lvm] cannot extend lv

[Rainer.Lay]

My idea was not to make a 4 stripe set with 4 PV, but a 2 stripe set:

stripe1: aaaaaaaaabbbbbb
stripe2: cccccccccdddddd

so if PV a and c are full, PV b and d are used.

I would create a new lv as you suggested, but drives a and c are two 
times bigger than b and d, so I thought about the above solution.

Rainer

>> I have a vg (data) with four drives /dev/sd[b-e]1
>> I created a 2 stripes lv (data1) with sd[bc]1
>                 ^^^^^^^
> 
> You cannot extend striped lvs onto new pvs. Even on the
> same physical hardware.  Once you have striped it, you are
> tied to the pvs used.
> 
> If you think about it, this makes sense, as otherwise you
> have some stripes containing more data than others.  In fact,
> as soon as the smallest pv is full, you will not be able to
> extend the lv, even if there is room in the other pvs.
> 
> If you want to have the filesystem striped over all the disks, you
> will need to create a new lv which is striped across them all,
> transfer the data to it, delete the old lv and then extend the
> new one.
> 
> Backups highly recommended.
> 
> Michael

Re: [linux-lvm] cannot extend lv

[idsfa]

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On Sun, Jan 19, 2003 at 10:16:04AM +0000,
Rainer.Lay@informatik.uni-erlangen.de wrote:
> My idea was not to make a 4 stripe set with 4 PV, but a 2 stripe set:
> 
> stripe1: aaaaaaaaabbbbbb
> stripe2: cccccccccdddddd
> 
> so if PV a and c are full, PV b and d are used.

Striping doesn't work that way.  It stripes across all pvs EVENLY
to improve access speeds (the whole reason to stripe).  The only
way to do what you want would have been to use kernel RAID to combine
the physical devices into a single logical device before creating the
stripe set.

> I would create a new lv as you suggested, but drives a and c are two 
> times bigger than b and d, so I thought about the above solution.

I understand, I went through the same exercise two months ago.  I
borrowed a disk from a friend, moved all of the data to it, and rebuilt
my whole VG setup.  It was a major pain in the neck.

Michael
-- 
Think Locally, Act Globally:  
"It's cold in here ... I'd better release a few million tons of CFCs!"

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Re: [linux-lvm] cannot extend lv

[Alasdair G Kergon]

On Sun, Jan 19, 2003 at 12:07:53PM -0600, idsfa@visi.com wrote:
> The only
> way to do what you want would have been to use kernel RAID to combine
> the physical devices into a single logical device before creating the
> stripe set.

Or try out LVM2 which no longer imposes these restrictions when
extending striped volumes.  (You can vary the number of stripes and the
stripesize.)

Alasdair
-- 
agk@uk.sistina.com

Re: [linux-lvm] cannot extend lv

[Steven Lembark]

> I understand, I went through the same exercise two months ago.  I
> borrowed a disk from a friend, moved all of the data to it, and rebuilt
> my whole VG setup.  It was a major pain in the neck.

But it's the only way. This is not unique to Sistina's
implementation. Once the filesystem has been striped at
a low level (vs. lvextending it to alternate disks at
the extent level) there isn't any good way to move the
sripes around.

I'd suggest picking up a backup device, though, instead
of a diskdrive. The last thing you need is for a borrowed
drive to croak while you're re-arranging the PV's.

--
Steven Lembark                               2930 W. Palmer
Workhorse Computing                       Chicago, IL 60647
                                            +1 773 252 1080