* [linux-lvm] size of lvm metadata
@ 2020-09-16 15:50 Tomas Dalebjörk
2020-09-17 15:21 ` Heinz Mauelshagen
0 siblings, 1 reply; 4+ messages in thread
From: Tomas Dalebjörk @ 2020-09-16 15:50 UTC (permalink / raw)
To: linux-lvm
hi
I am trying to understand how big the lvm metadata is
in the vgcfgbackup file, I can see
extent_size = 8192
dev_size = 204800
pe_start = 2048
pe_count 24
pe_count(24) * extent_size(8192) = 196608 bytes usable space of the total dev_size(204800)
metadata size? = dev_size(204800) - 196608 = 8192
but...
pe_start is 2048?
so what is pe_start here? cant be sectors(512)? bytes? well than ther be not aligned
so where starts the actual data?
and where ends the lvm metadata?
regards Tomas
Sent from my iPhone
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] size of lvm metadata
2020-09-16 15:50 [linux-lvm] size of lvm metadata Tomas Dalebjörk
@ 2020-09-17 15:21 ` Heinz Mauelshagen
2020-09-17 17:13 ` Tomas Dalebjörk
2021-12-19 20:13 ` Tomas Dalebjörk
0 siblings, 2 replies; 4+ messages in thread
From: Heinz Mauelshagen @ 2020-09-17 15:21 UTC (permalink / raw)
To: linux-lvm, tomas.dalebjork
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Tomas,
the first PE starts at offset 2048 sectors of size 512 bytes by default,
i.e. the LVM MDA (metadata area)
is ~1MiB big (because the MDA starts at offset 1 page into the device).
If you plan for large numbers of LVs or expect very scattered
allocations which both grow the metadata, you may want to create a
bigger MDA using vgcreate's option --metadatasize (also see
/etc/lvm/lvm.conf description on
metadata/pvmetadatasize).
On 9/16/20 5:50 PM, Tomas Dalebjörk wrote:
> hi > > I am trying to understand how big the lvm metadata is > > in the
vgcfgbackup file, I can see extent_size = 8192 dev_size = > 204800
pe_start = 2048 pe_count 24 > > pe_count(24) * extent_size(8192) =
196608 bytes usable space of the > total dev_size(204800) metadata size?
= dev_size(204800) - 196608 = > 8192 > > but... pe_start is 2048? so
what is pe_start here? cant be > sectors(512)? bytes? well than ther be
not aligned > > so where starts the actual data? and where ends the lvm
metadata?
At offset 2048 sectors (1MiB into the device) / MDA ends at sector 2047.
Mind that lvm2 metadata is text formatted (see /etc/lvm/backup/$VGName
for one)
and thus varies in size (the MDA is used as a ring buffer for 2 copies
of the MDA to
support atomic updates). As pointed out above when refering to
'vgcreate --metadatasize',
in more elaborate setups you may run out of MDA space.
Heinz
> > regards Tomas Sent from my iPhone > > >
_______________________________________________ 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/
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] size of lvm metadata
2020-09-17 15:21 ` Heinz Mauelshagen
@ 2020-09-17 17:13 ` Tomas Dalebjörk
2021-12-19 20:13 ` Tomas Dalebjörk
1 sibling, 0 replies; 4+ messages in thread
From: Tomas Dalebjörk @ 2020-09-17 17:13 UTC (permalink / raw)
To: Heinz Mauelshagen; +Cc: linux-lvm
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ok
Ithanks
> pe_count(24) * extent_size(8192) = 196608 bytes usable space of the
> > total dev_size(204800) metadata size? = dev_size(204800) - 196608 =
> > 8192
Sent from my iPhone
> On 17 Sep 2020, at 17:22, Heinz Mauelshagen <heinzm@redhat.com> wrote:
>
> Tomas,
>
> the first PE starts at offset 2048 sectors of size 512 bytes by default, i.e. the LVM MDA (metadata area)
> is ~1MiB big (because the MDA starts at offset 1 page into the device). If you plan for large numbers of LVs or expect very scattered allocations which both grow the metadata, you may want to create a
> bigger MDA using vgcreate's option --metadatasize (also see /etc/lvm/lvm.conf description on
> metadata/pvmetadatasize).
>
> On 9/16/20 5:50 PM, Tomas Dalebjörk wrote:
> > hi
> >
> > I am trying to understand how big the lvm metadata is
> >
> > in the vgcfgbackup file, I can see extent_size = 8192 dev_size =
> > 204800 pe_start = 2048 pe_count 24
> >
> > pe_count(24) * extent_size(8192) = 196608 bytes usable space of the
> > total dev_size(204800) metadata size? = dev_size(204800) - 196608 =
> > 8192
> >
> > but... pe_start is 2048? so what is pe_start here? cant be
> > sectors(512)? bytes? well than ther be not aligned
> >
> > so where starts the actual data? and where ends the lvm metadata?
> At offset 2048 sectors (1MiB into the device) / MDA ends at sector 2047.
>
> Mind that lvm2 metadata is text formatted (see /etc/lvm/backup/$VGName for one)
> and thus varies in size (the MDA is used as a ring buffer for 2 copies of the MDA to
> support atomic updates). As pointed out above when refering to 'vgcreate --metadatasize',
> in more elaborate setups you may run out of MDA space.
>
> Heinz
>
> >
> > regards Tomas Sent from my iPhone
> >
> >
> > _______________________________________________ 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/
>
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^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [linux-lvm] size of lvm metadata
2020-09-17 15:21 ` Heinz Mauelshagen
2020-09-17 17:13 ` Tomas Dalebjörk
@ 2021-12-19 20:13 ` Tomas Dalebjörk
1 sibling, 0 replies; 4+ messages in thread
From: Tomas Dalebjörk @ 2021-12-19 20:13 UTC (permalink / raw)
To: Heinz Mauelshagen; +Cc: linux-lvm
[-- Attachment #1.1: Type: text/plain, Size: 2254 bytes --]
Hi
if I have a disk that are merged into a server coming from another server containing a lvm snapshot
How can I convert this foreign disk to an existing lv volume?
The documentation says I can use
lvconvert-Zn -s targetvg/targetlv sourcevg/sourcelv
But I guess I have to perform some lvm metadata recreation first?
please let me know what steps are neede
Regards Tomas
Sent from my iPhone
> On 17 Sep 2020, at 17:22, Heinz Mauelshagen <heinzm@redhat.com> wrote:
>
> Tomas,
>
> the first PE starts at offset 2048 sectors of size 512 bytes by default, i.e. the LVM MDA (metadata area)
> is ~1MiB big (because the MDA starts at offset 1 page into the device). If you plan for large numbers of LVs or expect very scattered allocations which both grow the metadata, you may want to create a
> bigger MDA using vgcreate's option --metadatasize (also see /etc/lvm/lvm.conf description on
> metadata/pvmetadatasize).
>
> On 9/16/20 5:50 PM, Tomas Dalebjörk wrote:
> > hi
> >
> > I am trying to understand how big the lvm metadata is
> >
> > in the vgcfgbackup file, I can see extent_size = 8192 dev_size =
> > 204800 pe_start = 2048 pe_count 24
> >
> > pe_count(24) * extent_size(8192) = 196608 bytes usable space of the
> > total dev_size(204800) metadata size? = dev_size(204800) - 196608 =
> > 8192
> >
> > but... pe_start is 2048? so what is pe_start here? cant be
> > sectors(512)? bytes? well than ther be not aligned
> >
> > so where starts the actual data? and where ends the lvm metadata?
> At offset 2048 sectors (1MiB into the device) / MDA ends at sector 2047.
>
> Mind that lvm2 metadata is text formatted (see /etc/lvm/backup/$VGName for one)
> and thus varies in size (the MDA is used as a ring buffer for 2 copies of the MDA to
> support atomic updates). As pointed out above when refering to 'vgcreate --metadatasize',
> in more elaborate setups you may run out of MDA space.
>
> Heinz
>
> >
> > regards Tomas Sent from my iPhone
> >
> >
> > _______________________________________________ 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/
>
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_______________________________________________
linux-lvm mailing list
linux-lvm@redhat.com
https://listman.redhat.com/mailman/listinfo/linux-lvm
read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-09-16 15:50 [linux-lvm] size of lvm metadata Tomas Dalebjörk
2020-09-17 15:21 ` Heinz Mauelshagen
2020-09-17 17:13 ` Tomas Dalebjörk
2021-12-19 20:13 ` Tomas Dalebjörk
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