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I'm testing EBS volumes, trying to figure out how to achieve the advertised speed. Amazon says io1 volumes can do 1000MBps or 64,000 IOPS at 16K. I'm not seeing any higher than 600MBps. This is an m5n.2xlarge instance (with Nitro card) with a volume provisioned for 1280GB and 64000 IOPS.

When I write zeroes with dd, iostat shows consistent 100% utilization.

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
nvme1n1           0.00     0.00    0.00 2284.00     0.00   571.00   512.00    15.36    7.19    0.00    7.19   0.44 100.00

I tried using XFS filesystem on a partition aligned optimal with parted. I also tried dd writing directly to the block device nvme1n1. Performance is about the same either way.

For this test, I'm writing with dd using 1MB block size:

# dd if=/dev/zero of=/mnt/data/testfile bs=1M

What I don't understand is why I get nearly the same result if I write 4K blocks:

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await r_await w_await  svctm  %util
nvme1n1           0.00     0.00    0.00 2284.00     0.00   571.00   512.00    15.02    7.02    0.00    7.02   0.44 100.00
Elliott B
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1 Answers1

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dd if=/dev/zero of=/mnt/data/testfile bs=1

Its been a while since i used linux, but I'm 99% sure that bs argument is in bytes. So you I believe you are sending 1byte block size, instead of 1MB

Try this instead:

dd if=/dev/zero of=/mnt/data/testfile bs=1M

kamil234
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