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
_______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
