[linux-lvm] Is there a maximum for LV?

[linux-lvm] Is there a maximum for LV?

[Yanick Quirion]

Hi,

On the past I was using lvm 1.1rc2. For an unknown reason, the version is not anymore available.
But with this version, when I do a "vgdisplay" I was able to saw the LV Max Size:

[moonlight]:/# vgdisplay    
--- Volume group ---
VG Name               vg1 
VG Access             read/write
VG Status             available/resizable
VG #                  1
MAX LV                255
Cur LV                1
Open LV               1
MAX LV Size           1023.97 GB  <----------
Max PV                255
Cur PV                2
Act PV                2
VG Size               254.31 GB
PE Size               16 MB
Total PE              16276
Alloc PE / Size       16276 / 254.31 GB
Free  PE / Size       0 / 0
VG UUID               31iNWK-Ario-C4tq-yQNi-sGVk-gGs0-CjVV7T

How I'm testing LVM2. The field "MAX LV Size" is not there anymore. Is this means that LV doesn't have a maximum?

Output from LVM2:
[neptune]:/u# lvm vgdisplay vg02
  /dev/cdrom: open failed: Read-only file system
  --- Volume group ---
  VG Name               vg02
  System ID             localhost.localdomain1070620502
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  18
  VG Access             read/write
  VG Status             resizable
  MAX LV                256
  Cur LV                1
  Open LV               1
  Max PV                256
  Cur PV                2
  Act PV                2
  VG Size               50.86 GB
  PE Size               4.00 MB
  Total PE              13019
  Alloc PE / Size       13019 / 50.86 GB
  Free  PE / Size       0 / 0   
  VG UUID               Rw0ckX-GCd2-vlyF-KSWf-Q5tg-Qp2u-0Qjc7E


I just want to make sure that my configuration is all set to support very large LV.

Thanks again for your precious help!

Regards!

-----------
Yanick Quirion
Administrateur Réseau/Network Manager
NEOKIMIA INC.
Institut de Pharmacologie de Sherbrooke
3e étage (Édifice Z5)
3001 12e avenue Nord
Sherbrooke, Québec
CANADA
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email: Yanick.Quirion@neokimia.com

Re: [linux-lvm] Is there a maximum for LV?

[Jose Luis Domingo Lopez]

On Tuesday, 09 December 2003, at 09:29:05 -0500,
Yanick Quirion wrote:

> On the past I was using lvm 1.1rc2. For an unknown reason, the version is not anymore available.
> But with this version, when I do a "vgdisplay" I was able to saw the LV Max Size:
> 
> How I'm testing LVM2. The field "MAX LV Size" is not there anymore. Is this means that LV doesn't have a maximum?
> 
From vgcreate(8):
-s, --physicalextentsize PhysicalExtentSize[kKmMgGtT]
       Sets the physical extent size on physical volumes of this volume
       group.  A size suffix (k for kilobytes up to t for terabytes) is
       optional, megabytes is the default  if  no  suffix  is  present.
       Values  can be from 8 KB to 16 GB in powers of 2. The default of
       4 MB causes maximum LV sizes of ~256GB because as many  as  ~64k
       extents  are  supported  per LV. In case larger maximum LV sizes
       are needed (later), you need to set the  PE  size  to  a  larger
       value  as  well.  Later changes of the PE size in an existing VG
       are not supported.

So it seems you have a 255 GiB limit on LV sizes with your LVM2 setup. This
same limitation is what applies to LVM2 Logical Volumes, and the math is
simple to do.

Greetings.

-- 
Jose Luis Domingo Lopez
Linux Registered User #189436     Debian Linux Sid (Linux 2.6.0-test10-mm1)

Re: [linux-lvm] Is there a maximum for LV?

[Alasdair G Kergon]

> > How I'm testing LVM2. The field "MAX LV Size" is not there anymore. Is this means that LV doesn't have a maximum?
Correct: Provided you use the new "lvm2" metadata format, you're 
limited only by disk space and the maximum device size that your kernel
will support.

> >From vgcreate(8):
> -s, --physicalextentsize PhysicalExtentSize[kKmMgGtT]

> So it seems you have a 255 GiB limit on LV sizes with your LVM2 setup.
That section now only applies to PVs in "lvm1" format.
It needs updating...

For tool performance reasons it's still a good idea to use large 
physical extent sizes for large volume groups.  (This will get 
fixed eventually.)

Alasdair
-- 
agk@uk.sistina.com

Re: [linux-lvm] Is there a maximum for LV?

[AJ Lewis]

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On Dec 9, 2003, at 1:26 PM, Jose Luis Domingo Lopez wrote:
> On Tuesday, 09 December 2003, at 09:29:05 -0500,
> Yanick Quirion wrote:
>
>> On the past I was using lvm 1.1rc2. For an unknown reason, the 
>> version is not anymore available.
>> But with this version, when I do a "vgdisplay" I was able to saw the 
>> LV Max Size:
>>
>> How I'm testing LVM2. The field "MAX LV Size" is not there anymore. 
>> Is this means that LV doesn't have a maximum?
>>
> From vgcreate(8):
> -s, --physicalextentsize PhysicalExtentSize[kKmMgGtT]
>        Sets the physical extent size on physical volumes of this volume
>        group.  A size suffix (k for kilobytes up to t for terabytes) is
>        optional, megabytes is the default  if  no  suffix  is  present.
>        Values  can be from 8 KB to 16 GB in powers of 2. The default of
>        4 MB causes maximum LV sizes of ~256GB because as many  as  ~64k
>        extents  are  supported  per LV. In case larger maximum LV sizes
>        are needed (later), you need to set the  PE  size  to  a  larger
>        value  as  well.  Later changes of the PE size in an existing VG
>        are not supported.
>
> So it seems you have a 255 GiB limit on LV sizes with your LVM2 setup. 
> This
> same limitation is what applies to LVM2 Logical Volumes, and the math 
> is
> simple to do.

Actually, LVM2 no longer has a limitation on LV size based on PE size 
when using format2 metadata (which is used by default when creating new 
VGs).  So Yanick is correct in surmising the LV no longer has a maximum 
in LVM2 if the VG and LVs in question were created with the lvm2 tools. 
  If the VG was made with LVM1, or was created with the -M1 flag to 
vgcreate in LVM2, it does indeed still have the limit imposed by the 
format1 metadata.

Regards,
--
AJ Lewis
Sistina Software Inc.             http://www.sistina.com
720 Washington Ave, Suite 200     Voice:  612-638-0500
Minneapolis, MN 55414             E-Mail: 
lewis_NOSPAM_(AT)sistina(DOT)com

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--
AJ Lewis
Sistina Software Inc.             http://www.sistina.com
720 Washington Ave, Suite 200     Voice:  612-638-0500
Minneapolis, MN 55414             E-Mail: 
lewis_NOSPAM_(AT)sistina(DOT)com

Current GPG fingerprint = D638 9C01 D08F 29A4 5D50  D064 F6A6 0ED6 E386 
E6EB
Grab the key at: http://people.sistina.com/~lewis/gpg.html or one of the
many keyservers out there...

Chaos, panic, pandemonium - my work here is done

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