Re: large scale (audio) file I/O on OS X : help or insight requested
Re: large scale (audio) file I/O on OS X : help or insight requested
- Subject: Re: large scale (audio) file I/O on OS X : help or insight requested
- From: Hamilton Feltman <email@hidden>
- Date: Wed, 11 Mar 2015 20:08:46 -0700
> On Mar 11, 2015, at 6:53 PM, Paul Davis <email@hidden> wrote:
>
> robin reports back that your dd-tester gives:
>
> 41.1806 MB/sec write
> 42.6064 MB/sec read
>
> (Western Digital 6400AAV - we can't find specs online)
>
> He also tried it formatted as FAT32, with essentially no change in the results.
>
Ok, this is enough information to calculate if your drive is performing within spec. Looking at the first example (block size 65536)
From your test:
$ ./run-readtest.sh -f 10 -d /Volumes/OSXext/disktest/ 65536 131072 4096000
# Building files for test...
# Blocksize 65536
# Min: 8.9910 MB/sec Avg: 9.4645 MB/sec || Max: 0.890 sec
# Max Track count: 51 @ 48000SPS
# Sus Track count: 49 @ 48000SPS
65536 8.9910 9.4645 0.8898 0.00912
So:
file size: 10485760
num files: 128
total bytes: 1342177280
seeks = 1342177280 / 65536
seeks: 20480
total_time: 270.484
Drive reports:
42.6064 MB/sec read (44676048 bytes/sec)
Time required to stream 1342177280 bytes -> 30.04 seconds
Blocksize 65536
Number of seeks 20480
Time taken: 270.484 seconds
Time available for seeks: 270.484 - 30.04 = 240.444 seconds
240.444 / 20480 -> 11.74 ms seek time
Out of 270 seconds it took to read the 1.25GB, the drive had to spend 240 seconds performing 20480 seeks, with an average seek time of 11.74 milliseconds.
This drive seems to be performing well.
Regards,
Hamilton
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