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Re: [linux-lvm] How do you create large numbers of LVs? (In the 1000s) Is it even possible?



I know that a similar bug (158687) has been fixed since your version... It is a somewhat similar bug, but I think the previously mentioned applies to you more. Still, it couldn't hurt to update.

  brassow

On Jul 28, 2005, at 4:26 PM, Ming Zhang wrote:

I did vgchange -an vg1

and then still fail

[root fc3-i386-2 ~]# lvcreate -L12M -ntv282 vg1
  VG vg1 metadata writing failed
[root fc3-i386-2 ~]# lvcreate -vvvvv -L12M -ntv282 vg1
      Setting global/locking_type to 1
      Setting global/locking_dir to /var/lock/lvm
      File-based locking enabled.
      Getting target version for linear
        dm version
        dm versions
      Getting target version for striped
        dm versions
      Locking /var/lock/lvm/V_vg1 WB
    Finding volume group "vg1"
        Opened /dev/sda
      /dev/sda: No label detected
        Opened /dev/md0
        /dev/md0: Failed to read label area
        Opened /dev/sda1
      /dev/sda1: No label detected
        Opened /dev/sda2
      /dev/sda2: No label detected
        Opened /dev/sda3
      /dev/sda3: No label detected
        Opened /dev/sdb
      /dev/sdb: No label detected
        Opened /dev/sdb1
      /dev/sdb1: lvm2 label detected
      /dev/sdb1: lvm2 label detected
        Read vg1 metadata (710) from /dev/sdb1 at 50688 size 65377
    Creating logical volume tv282
        Allowing allocation on /dev/sdb1 start PE 843 length 180
    Archiving volume group "vg1" metadata.
  VG vg1 metadata writing failed
      Unlocking /var/lock/lvm/V_vg1
        Closed /dev/sda
        Closed /dev/md0
        Closed /dev/sda1
        Closed /dev/sda2
        Closed /dev/sda3
        Closed /dev/sdb
        Closed /dev/sdb1

i use this script to create them

#!/bin/bash
# a simple loop to create large # of LV

LIMIT=300
a=1

while [ "$a" -le $LIMIT ]
do
        lvcreate -L10M -ntv$a vg1
        free
        let "a+=1"
done

not ram problem


[root fc3-i386-2 ~]# free total used free shared buffers cached Mem: 255044 80704 174340 0 17776 47400 -/+ buffers/cache: 15528 239516 Swap: 522104 0 522104

[root fc3-i386-2 ~]# lvextend --version
  LVM version:     2.00.25 (2004-09-29)
  Library version: 1.00.19-ioctl (2004-07-03)
  Driver version:  4.4.0

shall i try new version?

ming


On Thu, 2005-07-28 at 15:49 -0500, Jonathan E Brassow wrote:
yeah...  it could be a memory issue which is causing the difference in
active lvs.

It could be the fact that he starts with _inactive_ lvs that allows him
to create so many to start.


To see if you are experiencing the same bug, you could 'vgchange -an
<vol_name>' and then try to create a bunch of lvs...  Then, once
created, try to activate them.

  brassow

On Jul 28, 2005, at 3:38 PM, Ming Zhang wrote:

i think this is strange that this guy can at least create 1500 lv but
fail to activate them all.

here what i found is i even can not create ~300 lv.


ming


On Thu, 2005-07-28 at 15:32 -0500, Jonathan E Brassow wrote:
I think the problem you are seeing is similar to the one found in
bugzilla (164198). Would you be willing to add some notes there? It
will give you a place to track the progress...


https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=164198

  brassow

On Jul 28, 2005, at 2:18 PM, Ming Zhang wrote:

On Thu, 2005-07-28 at 12:09 -0700, Nathaniel Stahl wrote:
We'd like to be able to create a large number of LVs (potentially
numbering in the low thousands). I get failure after LV 226 or so,
though - "VG VolGroup01 metadata writing failed".


RedHat claims this should be possible with LVM2 on the following web
page:


http://www.redhat.com/magazine/009jul05/features/lvm2/

I admit to being a little suprised at the 2^32 max LV claim - I was
figuring 2^20 as the theoretical max given 2.6's 32 bit device
numbering
scheme (20 bits for minor, 12 bits for major).


The LVM2 code, at least version 2.00.25 as distributed in FC3,
appears
to have a check that the minor number is strictly less than 256.
Removing this check allows for the creation of working LVs using
minors
greater than 256, but LV creation fails with the error "VG
VolGroup01
metadata writing failed" creating the 227th LV. Even with the minor
limit in place - I can't create more than 226 LVs.

i asked this question before. there is a hard coded limitation in lvm
metadata, so the real number is like this, limited around 2xx. the
limitation will be removed in near future. how near? i do not know.
:)




Is there a patch that allows this limit to be broken? Should I be using a newer version of the tools? If not currently possible, is this something that will be in the near future?

Thanks for any help/advice you can give.

-Nate Stahl

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