LVM Version 2.0 Volume Groups in HP-UX 11i v3 (September 2008)

The last factor is related to resynchronization time. Small extent size can accelerate the resynchronization of a
logical volume in the case where an application issues sparse I/Os on the logical volume at the time a physical
volume is down. In this case, the amount of data to resynchronize is smaller. As a result, the resynchronization is
faster. Note that if a resynchronization of a complete mirror of a logical volume is needed, the size of the extent
has no affect on the resynchronization time.
In general, unless you need a lot of very small logical volumes, it is better to pick a large extent size and use
striped logical volumes where you need high performance.
The following table illustrates how extent size limits maximum volume group size.
Maximum volume group size versus extent size
0.1
0.44
1.85
7.57
30.6
123.02
491.44
510 510
32
64
128
256
512
1024
2048 2048 2048
0.1
1
10
100
1000
10000
1 2 4 8 16 32 64 128 256
extent size in mb
Maximum volume
Group size in tb
1.0 volume group
2.x volume group
Figure 2
Notes:
• The 2.x graph stops at 2048 TB because of the limit of 32 million extents per volume group.
• The 1.0 graphs stops at 510 TB because the metadata must fit in one extent.
Memory Footprint
The memory footprints given in this chapter are estimates.
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