Disk overloaded throttling

[boomman]

I have latest stable utorrent 3.2.29126.

It throttles the download to fraction of my actual speed because the "disk is overloaded" while it most certainly isn't.

See this screenshot, all downloads go to disk D: and while it does have spikes of 60%, most of the time it is sitting there with 0% load.

Please advise.

[ciaobaby]

And is disc 'D' an external device?

[boomman]

And is disc 'D' an external device?

No. Internal WD drive.

[ciaobaby]

Few things to try

first is set cache size to 256 in Preferences -> Advanced -> Disk Cache

[boomman]

The problem was apparently disabled write cache. After I enabled it it stopped throttling.

I am not sure why would it cause this problem.

[boomman]

Noooow I remember why I disabled it.

With write cache it works well first several minutes and then starts to ACTUALLY crash my HDD with 100% load.

[boomman]

I did alleviate the problem somewhat by changing diskio.max_write_queue to 320 and increasing "coalesce" writes tenfold, but looking at procmon, I have no idea what this crazy program does anymore.

Judging from log, it executes the same write on same file twice with different offsets and one write is buffered while another one is unbuffered. These make zero sense to me, I would be happy if could explain what the hell is going on here.

I would also be very happy to just disable ALL of internal caching in utorrent and let windows write writes at its own pace, but I am apparently not able to disable all of those.

[ciaobaby]

increasing "coalesce" writes tenfold

So you set it to TWENTY Megabytes per second and think that will help???

diskio.coalesce_write_size: This option determines the size threshold for which µTorrent should write data out coalesced, and is relevant only if diskio.coalesce_writes is enabled. This value is interpreted in bytes per second, so please enter it as such.

The default is 2097152 bytes per second if you need commas 2,097,152 B/s (2MB), it's somewhat unlikely that increasing the write rate is going to reduce drive overloading.

You need to write at a lower rate, so a smaller cache means less data being pushed through an interface that cannot handle. YOU have to start at LOW DATA rates and work upwards to a point of overloading THEN throttle back until it stops

There are plenty of settings to adjust, read the manual for all the diskio settings and what they mean and do.

[boomman]

I may be missing something here, but here's description of the setting

diskio.coalesce_writes: This option tells µTorrent to try to minimize the number of writes to disk by writing more data at once. It doesn't have any effect on download speeds, but might increase memory and CPU usage to achieve less disk writes.

Isn't it just another kind of cache? The way I read it is program delays writes until it downloads coalesce_write_size amount of data and then writes it all at once.

And taking into account that utorrent writes every write to disk twice for some reason it is better as much data as possible to avoid crashing hdd frequent small writes.

The point is increasing both settings did help. It still overloads to 100% at times, but I was able to get stable 9 MBps out of utorrent.