Usable space in PV
Task: calc usable space of PV before create PV and before create partition for PV.
In my experiments usable space in PV = PVSize / ExtentSize * ExtentSize with integer operations. But when Metadata may be large - when LVM have a lot of logical volumes and it can take more space.
I found in /etc/lvm/lvm.conf parameter pvmetadatasize = 255 secotors (default). What will if metadata will grow to more then 255 sectors?
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Timofey Koolin
Dne 30.9.2015 v 17:28 Timofey Koolin napsal(a):
Quoted 11 lines
Task: calc usable space of PV before create PV and before create partition for PV.
In my experiments usable space in PV = PVSize / ExtentSize * ExtentSize with integer operations.
But when Metadata may be large - when LVM have a lot of logical volumes and it can take more space.I found in
/etc/lvm/lvm.confparameter pvmetadatasize = 255 secotors (default). What will if metadata will grow to more then 255 sectors?
If you plan to host lots of LVs within a single VG (in range of hundreds)
use i.e. 'pvcreate --metadatasize 5M'
(i.e. ~7000 linear single segment LVs takes around 2.2MB and you need space for at least 2 metadatas to fit in)
What I'm not quite sure is your 'task' - what's the purpose ?
Do you want to do some 'sector' precise emulation of what lvm2 is doing by watching resuls of couple command with just subset of it's options ?
Isn't better to read man pages ?
Zdenek
Task - problem.
I make universal extender of filesystem (for example extend fs in virtual computer after resize disk or add space to filesystem in hosting server, etc.). Before extend volume group and filesystem I want to make plan of extends. For plan I need to know how many bytes it can add to VG from disk/partition. I know size of disk, partition, free space - and I have to know free space after create PV on free space of disk. I don't know how many LV will be on target system (system, which run fsextender), I don't know fragmentation of it and etc.
Is any way to know how many space take metadata and how many space will be usable?
Quoted 30 lines · Zdenek Kabelac
Dne 30.9.2015 v 17:28 Timofey Koolin napsal(a):
Quoted 11 lines
Task: calc usable space of PV before create PV and before create partition for PV.
In my experiments usable space in PV = PVSize / ExtentSize * ExtentSize with integer operations.
But when Metadata may be large - when LVM have a lot of logical volumes and it can take more space.I found in
/etc/lvm/lvm.confparameter pvmetadatasize = 255 secotors (default). What will if metadata will grow to more then 255 sectors?If you plan to host lots of LVs within a single VG (in range of hundreds)
use i.e. 'pvcreate --metadatasize 5M'
(i.e. ~7000 linear single segment LVs takes around 2.2MB and you need space for at least 2 metadatas to fit in)What I'm not quite sure is your 'task' - what's the purpose ?
Do you want to do some 'sector' precise emulation of what lvm2 is doing by watching resuls of couple command with just subset of it's options ?Isn't better to read man pages ?
Zdenek
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Timofey Koolin