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High download kills my uploads


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I have problem with my upload practically going to 0 when I download at high speed. This usually happens when I download at 5+ MB/s.

After ~30 sec the download is finished or I stop it the upload goes back to normal speed.

I doubt this is my ISP's fault. I'm thinking hardware, maybe the HDDs can't handle it?

I have 4 HDDs.

HDD1 IDE - WinXP partition

HDD1 partition 2




Today I saw the upload getting back to a few 100 kB after 2-3 min of upload being at 0, while I was still downloading at 10 MB/s.

Here you can see that on the second download the upload drops to 0, which is what practically always happens. On the 1st download it stayed up for a few 100 kB/s (but still dropped in speed) which rarely happens:


Maybe the HDD statistics can help too?:


TCP Optimizer setting

Set to MAX, 20 Mbps setting.

Color of the network status light in µTorrent's status bar (at the bottom of the µTorrent main window)


What the Speed Guide shows your settings to be?


What you have net.max_halfopen set to?

30, TCPIP.SYS is set to 50 with the patch

Operating system installed

WinXP Pro

Security software installed

AntiVir AV

Exact router model(s), and exact modem model

No router used.

Connection type

fiber, 100/100 Mbps

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TCP Optimizer doesn't do anything you should be doing to your connection.... or configuring uT. If you're using 1.7 it sounds like Windows Cacheing. There is a new 1.8 beta out in the Announcements forum which allows disabling this windows cache and people with such an awesome download speed as you seem to have success with. If you prefer to try setting it up you can use it self-contained and go to Ctrl-P -> Advanced -> Disk Cache and disable Windows Cache.

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No kidding... :( It sounds like you may need to enable ONE of the caches... which one works better you'll have to experiment on unless someone who knows checks in on this thread.

Sort of off topic, but have you tried setting an upload / download limit to see how that affects your sustained speeds and if it helps compensating for the seeming one-mindedness of your client?? I really have no experience with such awesome connections outside a LAN environment so don't know what else to try.

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My impression of the pictures is uTorrent's read and write RAM cache is totally underutilized, especially to be set at 1 GB. You probably need to change the settings in cache to force uTorrent to use the cache more heavily.

Also, there's a BUG in uTorrent...at least older versions should NOT be set beyond 1023 MB cache size.

...It's my guess that your line is almost half-duplex in nature, or your hard drive/s are overloading due to the random access reads/writes.

Have you tried downloading to 1 hard drive (or multiple hard drives) while trying to seed from another hard drive (preferably on a different HDD controller)?


Trying to interrupt someone else's message thread (thread hijacking) is highly frowned on here. You should make a NEW post and give FAR more information about what your internet connection is, what version/s of uTorrent you're trying to use, and what you've already tried.

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> overloading due to the random access reads/writes.

Aka "disk contention". Using a mirrored drive will help with read performance (RAID 1). Using a striped set (RAID 0) will improve write performance since you double the number of disk spindles that can write data to.


> I'm thinking hardware, maybe the HDDs can't handle it?

In Windows, there's an Admin Tool called "Performance". You can add Physical Disk, Current Disk Queue Length to see if there is any disk contention causing the zero upload.

Microsoft has a specific guide on how to Tune Disk Performance:


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