How to perform tests for writing 64 KB files? My Website allows users to upload picture files with an average of 64 KB per file.

If you want to know how your environment performs on writing 64 KB files, you can use the following SQLIO options:

• "-LS" - Sets SQLIO to report latency measurements using the system timer.
• "-kW" - Sets SQLIO to perform writing tests.
• "-b64" - Specifies test block size to 64 KB, which represents the average file size on your Website.
• "-i64" - Specifies the run size of 64 I/O tests. This simulates the pattern of users uploading 64 different files in row.
• "-f64" - Specifies the stripe factor of 64 blocks. This simulates the pattern of users uploading consecutive files stored 64-file away from each other.
• "-t1" - Sets SQLIO to use 1 thread only. This simulates the pattern of a quiet Website that users comes one after another sequentially.
• "-s300" - Sets SQLIO to run for 300 seconds, or 5 minutes.

Below is a test result SQLIO with above options on a Dell computer hard disk with Windows 8:

C:\fyicenter\SQLIO>sqlio -LS -kW -b64 -i64 -f64 -t1 -s300
        
1 thread writing for 300 secs to file testfile.dat
        using 64KB IOs over 4096KB stripes with 64 IOs per run
size of file testfile.dat needs to be: 268435456 bytes
initialization done
CUMULATIVE DATA:
throughput metrics:
IOs/sec:   487.31
MBs/sec:    30.45
latency metrics:
Min_Latency(ms): 0
Avg_Latency(ms): 1
Max_Latency(ms): 280
histogram:
ms: 0  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+
%: 59 13 11  6  3  3  1  1  0  0  1  1  0  0  0  0  0  0  0  0  0  0  0  0  0        

As you can see, this Dell computer is capable to write 487 files of 64 KB per second to the hard disk in a single thread without any buffering.

The average latency of writing a 64-KB block is about 1 milliseconds. In other words, your users should be able to upload a file to your Website in 1 millisecond if we ignore the impact of the Web server software.

Comparing to the data reading test in the previous tutorial, the result might be a surprise to many of us. This Dell computer writes data at a speed of 30.45 MBs/sec, but reads data at a speed of 8.77 MBs/sec. So writing data is 3.5 times faster than reading data!

Usually, hard disks are capable to read faster than write. But in the case of 64-KB block I/O tests, operating system caching mechanism helps writing more than reading. See next tutorials on performance impact of block size.

⇒ Windows Resource Monitor - Disk Writing Speed

⇐ Windows Resource Monitor - Disk Reading Speed

⇑ Tuning SQLIO for Your Environment

⇑⇑ SQLIO Disk I/O Benchmark Test Tutorials