Chapter 9. Advanced features for storage efficiency 471
File system problems can be moderated by tools, such as defrag, or by managing storage by
using host Logical Volume Managers (LVMs). The thin-provisioned volume also depends on
how applications use the file system. For example, some applications delete log files only
when the file system is nearly full.
There is no recommendation for thin-provisioned volumes. As explained previously, the
performance of thin-provisioned volumes depends on what is used in the particular
environment. For the best performance, use fully allocated volumes rather than
thin-provisioned volumes.
9.3.3 Limitations of virtual capacity
A few factors (extent and grain size) limit the virtual capacity of thin-provisioned volumes
beyond the factors that limit the capacity of regular volumes. Table 9-2 shows the maximum
thin provisioned volume virtual capacities for an extent size.
Table 9-2 Maximum thin provisioned volume virtual capacities for an extent size
Table 9-3 shows the maximum thin-provisioned volume virtual capacities for a grain size.
Table 9-3 Maximum thin volume virtual capacities for a grain size
Important: Do not use defrag on thin-provisioned volumes. The defragmentation process
can write data to different areas of a volume, which can cause a thin-provisioned volume to
grow up to its virtual size.
Extent size in
megabytes (MB)
Maximum volume real capacity
in gigabytes (GB)
Maximum thin virtual capacity
in GB
0,016 002,048 002,000
0,032 004,096 004,000
0,064 008,192 008,000
0,128 016,384 016,000
0,256 032,768 032,000
0,512 065,536 065,000
1,024 131,072 130,000
2,048 262,144 260,000
4,096 262,144 262,144
8,192 262,144 262,144
Grain size in KiB Maximum thin virtual capacity in GiB
032 0,260,000
064 0,520,000
128 1,040,000
256 2,080,000
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