[Tip] Create dummy files

fallocate & truncate & dd

create time : fallocate < truncate < dd

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$ time fallocate -l 10G 10gig

real 0m0.041s
user 0m0.000s
sys 0m0.001s
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$ time truncate -s 10G tengig

real 0m0.001s
user 0m0.001s
sys 0m0.000s
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$ time dd if=/dev/zero of=10gigfile bs=10G count=1
0+1 records in
0+1 records out
2147479552 bytes (2.1 GB, 2.0 GiB) copied, 17.3439 s, 124 MB/s

real 0m17.507s
user 0m0.000s
sys 0m1.825s
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create 10 X 1G dummy file

$ for i in {1..10}; do fallocate -l 1G 1G_$i; done
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