CODEWITHSUNDEEP
linuxiofilesystemsbenchmarkingiozone
Neal
Neal

Reputation: 141

What's the meaning of "Min xfer" and "throughput" in the output of IOzone

I'm a new user of IOzone, when I run the IOzone with the command: ./iozone -i 0 -i 1 -t 2 -T, it generates the following result(partially):

Command line used: ./iozone -i 0 -i 1 -t 2 -T
Output is in Kbytes/sec
Time Resolution = 0.000001 seconds.
Processor cache size set to 1024 Kbytes.
Processor cache line size set to 32 bytes.
File stride size set to 17 * record size.
Throughput test with 2 threads
Each thread writes a 512 Kbyte file in 4 Kbyte records

Children see throughput for  2 initial writers  =  650943.69 KB/sec
Parent sees throughput for  2 initial writers   =   13090.24 KB/sec
Min throughput per thread           =  275299.72 KB/sec 
Max throughput per thread           =  375643.97 KB/sec
Avg throughput per thread           =  325471.84 KB/sec
Min xfer                    =     356.00 KB

Children see throughput for  2 rewriters    = 1375881.50 KB/sec
Parent sees throughput for  2 rewriters     =   10523.74 KB/sec                                                
Min throughput per thread           = 1375881.50 KB/sec 
Max throughput per thread           = 1375881.50 KB/sec
Avg throughput per thread           =  687940.75 KB/sec
Min xfer                    =     512.00 KB

Children see throughput for  2 readers      = 2169601.25 KB/sec
Parent sees throughput for  2 readers       =   27753.94 KB/sec
Min throughput per thread           = 2169601.25 KB/sec 
Max throughput per thread           = 2169601.25 KB/sec
Avg throughput per thread           = 1084800.62 KB/sec
Min xfer                    =     512.00 KB

Children see throughput for 2 re-readers    = 2572435.25 KB/sec
Parent sees throughput for 2 re-readers     =   26311.78 KB/sec
Min throughput per thread           = 2572435.25 KB/sec 
Max throughput per thread           = 2572435.25 KB/sec
Avg throughput per thread           = 1286217.62 KB/sec
Min xfer                    =     512.00 KB

iozone test complete.

I get confused about meaning of "throughput" and "Min xfer", is there someone can help me? By the way, why the throughput seen from children and parent is different? Thanks!

Upvotes: 2

Views: 2703

Answers (1)

rbeede
rbeede

Reputation: 303

Min xfer refers to the smallest amount of data written at one time. "Each thread writes a 512 Kbyte file in 4 Kbyte records"

So if the Min xfer was 512.00 KB it wrote the entire actual file to disk at once (grouped all the 4 Kbyte records together).

Children and parent throughput are different due to OS I/O buffering. iozone doesn't force direct (non-buffered) read or writes with the throughput test. What you're really testing is your system's buffer cache + disk cache + disk speed combo.

Upvotes: 4

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