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[linux-lvm] understanding large LVM volumes



Hello.
I am trying to understand what the size limitations of VGs are for LVM2.
I am running 2.6.10-1.741_FC3smp, lvm2-2.00.25
The HOWTO document has really helped my understanding of the general concepts involved.


My goal is to create a 4+TB VG with current devices and then be able to expand this VG to 10+TB when new resources become available.

My questions are as follows. What is the maximum size of a single VG?
How does the Physical Extent size affect the maximum VG size?
How does one go about chosing a PE size for a VG?


Does anyone have experience with very large LVM VGs?
I want to ensure that I choose a good PE size when creating this large VG and that
I don't paint myself into a corner, making it difficult to grow to 10TB when the time
comes.


Any information, suggestions, or experiences for/with large volumes would
be much appreciated.

As a test, I created a VG with 3 devices totaling 4.3TB. I used only defaults.

[root damascus ~]# pvscan

PV /dev/sdc1 VG testvg lvm2 [431.99 GB / 0 free]

PV /dev/sdd1 VG testvg lvm2 [1.95 TB / 0 free]

PV /dev/sde1 VG testvg lvm2 [1.95 TB / 0 free]

Total: 3 [4.33 TB] / in use: 3 [4.33 TB] / in no VG: 0 [0 ]

[root damascus ~]# vgdisplay

--- Volume group ---

VG Name testvg

System ID

Format lvm2

Metadata Areas 3

Metadata Sequence No 3

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 1

Open LV 1

Max PV 0

Cur PV 3

Act PV 3

VG Size 4.33 TB

PE Size 4.00 MB

Total PE 1134586

Alloc PE / Size 1134586 / 4.33 TB

Free PE / Size 0 / 0

VG UUID hnKF8h-Infa-wKiE-KtUT-OByG-q0pe-Nd4taB


Thank you, Randall


-- ..:.:::: Randall Jones GST NASA Goddard Space Flight Center HPC Visualization Support http://hpcvis.gsfc.nasa.gov Scientific Visualization Studio http://svs.gsfc.nasa.gov rajones svs gsfc nasa gov Code 610.3 301-286-2239



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