Recording more multiple I/Q streams - query

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daveB
Posts: 1465
Joined: 07 Oct 2014 16:49

Recording more multiple I/Q streams - query

Post by daveB » 12 Jan 2020 15:41

I hope the subject heading is clear enough.

With the availabilty of 3 wideband SDRs I wanted to try recording more than one stream simultaneously to an external hard drive. I have also just purchased a 4TB USB 3.0 external hard drive to give more capacity (roughly 22 hrs for a 10 MHz wide bandwidth).

Here is the puzzle.
On my Samsung M3 2 TB portable drive I can record 2 x 8 MHz b/w streams without any dropped buffers. On my Maxtor 2 TB external drive I can't, and on my Seagate 4 TB hard drive I can't - loads of dropped buffers.

Here are the stats from Task Manager:
Samsung 2 TB HDD: 1 stream = 32.0 MB/s - 9% active time. 2 streams = 65 MB/s - 23% active time
Maxtor 2 TB HDD; 1 stream = 32.0 MB/s 21% active time. 2 streams= 30-57 MB/s - 100% active time
Seagate 2 TB HDD; 1 stream = 32.0 MB/s 23% active time. 2 streams= 65 MB/s - 100% active time

I've tried swapping the drives about - but the results are consistent. The Samsung M3 HDD can handle much higher throughput than the other two devices. It must be the something to do with the system configuration.

However - all is not lost - the much better performance of the Samsung drive means that I can stream 8MHz b/w through a USB 2.0 port with no dropped buffers.

Anyone any thoughts as to why the big difference - especially as both the Samsung and Maxtor devices identify as having an M3 drive, wwhich is made by Seagate.
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