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Test your total disk IO capacity, regardless of caching, to find out how fast the TRUE speed of your disks are

Terminal - Test your total disk IO capacity, regardless of caching, to find out how fast the TRUE speed of your disks are
time (dd if=/dev/zero of=blah.out bs=256M count=1 ; sync )
2009-07-14 20:19:23
User: tkunz
Functions: dd sync time
2
Test your total disk IO capacity, regardless of caching, to find out how fast the TRUE speed of your disks are

Depending on the speed of you system, amount of RAM, and amount of free disk space, you can find out practically how fast your disks really are. When it completes, take the number of MB copied, and divide by the line showing the "real" number of seconds. In the sample output, the cached value shows a write speed of 178MB/s, which is unrealistic, while the calculated value using the output and the number of seconds shows it to be more like 35MB/s, which is feasible.

Alternatives

There is 1 alternative - vote for the best!

Terminal - Alternatives
time dd if=/dev/zero of=blah.out oflag=direct bs=256M count=1
2009-07-15 07:17:32
User: olorin
Functions: dd time
0

Let dd use direct I/O to write directly to the disk without any caching. You'll encounter very different results with different block sizes (try with 1k, 4k, 1M, ... and appropriate count values).

Know a better way?

If you can do better, submit your command here.

What others think

nice but.. to play the real game use www.iozone.org or bonnie

Comment by ioggstream 276 weeks and 1 day ago

What you're doing here is really testing *filesystem* performance rather than disk IO. For actual "disk IO", do what ioggstream said or use hdparm:

hdparm -t /dev/sda

this will test drive throughput by actually streaming a write off the disk. Use the -T option to test how fast the cpu, memory, & linux disk buffer cache can theoretically go.

The underlying filesystem can

Comment by bwoodacre 276 weeks ago

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