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Lin Lin

Same amount of disk read as download speed [SOLVED]

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Posted (edited)

[Synopsis]

As BitComet downloads, it produces disk read activity at the same speed as download speed at that time.

 

[Setup]

BitCometBeta 20191225

 

[Steps to reproduce]

1. Set upload speed limit to a very low value such as 10KiB/s;

2. Download a popular torrent with BitComet;

3. Observe disk activity with any monitoring tool, such as perfmon or HWiNFO;

4. Repeat the above steps with qBitorrrent 4.1.9.1 and uTorrent 2.2.1.

 

[Actual behaviour]

As BitComet downloads, it produces disk read activity at the same speed as download speed at that time.

As shown in the perfmon screenshot below, the red line(Disk Read Bytes/sec) is almost overlapping with the yellow line(Disk Write Bytes/sec)

BitComet disk I/O graph

 

[Expected behaviour]

BitComet should not produce disk read activity at the same speed as download speed.

The disk I/O rate graph should look like this: (qBittorrent 4.1.9.1)

Notice that the the red line(Disk Read Bytes/sec) stays near the bottom.

qb4191.png.d7c2a1ff77837518cd556ac550fdac7f.png

 

Or this: (uTorrent 2.2.1)

Notice that the the red line(Disk Read Bytes/sec) stays near the bottom.

uTorrent 221 disk I/O graph

 

[Uneducated guesses]

uTorrent has an advanced option named diskio.smart_hash enabling piece hash calculation from cache before a finished piece is written to disk, thus avoiding re-reading the same piece back from the disk. I wonder if it's related or not? If BitComet does not possess a similar feature it would most probably cause the above described behaviour.

 

Thank in advance!

 

 

perfmon.png

Edited by cassie
Update images (see edit history)

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This issue has been acknowledged by the developer and fixed in the latest build. [1.64 beta2 - 20200110]

 

@Rhubarb  How to add [SOLVED] to the OP title? It's not possible to edit after 30 minutes.

Edited by Lin Lin (see edit history)

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